Palladium(II)-catalysed rearrangements of allylic acetates in the syntheses of methyl (10E,12Z)-9-hydroxyoctadeca-10,12-dienoate (alpha;-dimorphecolate) and (2E,4Z)-deca-2,4-dienal

摘要

J. CHEM. SOC. PERKIN TRANS. I 1988 2061 Palladium(ii)-catalysed Rearrangements of Allylic Acetates in the Syntheses of Methyl (1 0euro;,122)-9-Hydroxyoctadeca-I 0,12-dienoate (a-Dimorphecolate) and (2euro;,4Z)-Deca-2,4-dienal Martine M. L. Crilley, Bernard T. Golding," and Colin Pierpoint Department of Organic Chemistry, Bedson Building, The University, Ne wcastle upon Tyne, NEI 7RU Preparatively useful examples of the kinetically controlled Pdi I-catalysed rearrangement of (1 euro;,4Z) -3-acetoxy-I ,4-dienes into (2euro;,4Z) -1 -acetoxy-2,4-dienes are described. These include the conversion of (2euro;,5Z,8Z) -4-acetoxydeca-2,5,8-triene into (3euro;,5Z,8Z) -2-acetoxydeca-3,5,8-triene and steps in syntheses leading to the natural products 9-hydroxyoctadeca-I 0,12-dienoic acid (a-dimorphecolic acid, obtained as its methyl ester) and (2euro;,4Z)-deca-2,4-dienaI. Studies of a variety of substrates show that the order of reactivity of double bonds in the Pd"-catalysed rearrangement is euro;-disubstituted Z-disubstituted -vinyl a-methylvinyl.Pdo-catalysed rearrangements of these substrates proceed, in contrast to the Pdll -catalysed rearrangements, to thermodynamically control led product (s) ,e.g. the above triene gives main Iy (3euro;,5euro;,8Z) -2-acetoxydeca-3,5,8-triene. The rearrangement of (lE,42)-3-acetoxy-1,4-dienes into acetoxyhepta-2,5-diene is converted into OC' 'OMe(3E,5Z)-(2E,42)-1-acetoxy-2,4-dienes catalysed by certain Pd" com-2-acetoxyhepta-3,5-diene.,Hence, a plausible mechanism for plexes { e.~.bis(acetonitri1e)palladium dichloride, PdCI,-the rearrangement is as shown in Scheme 1, in which the (MeCN),} is a rapid, efficient, stereocontrolled process for formation of the E,Z-product is a kinetically controlled process substrates substituted at the 1- and 5-positions by alkyl groups favoured by a lower energy transition state leading to the (eg.Equation l).' intermediate drawn., The alternative intermediate and corre- sponding transition state are destabilised by a 1,3-diaxial interaction. In contrast, the rearrangement of substrates (la+) cata-1ysed by te trakis( trip heny lp hosphine)palladium(O) Pd( P h 3-P)J gives the thermodynamically stable E,E-products (e.g.Equation 1. Equation 2). The rearrangement of substrates (la+) occurs preferentially Pd( Ph 3P I, (cat .Iat the E-double bond to give mainly the products (2a-c), respectively. Using ''0 n.m.r.spectroscopy to monitor the OAcrearrangement it was shown that '70COMe-(2E,5Z)-4-Equation 2. dH The mechanism of this process, supported by a ''0-labelling study, was suggested to be a Pdo-assisted ionisation to acetate and a Pd-stabilised pentadienyl cation. These species recombine to afford the observed product (cJ: Scheme 2). Scheme 1. Mechanism (ref. 2) for the Pd"-catalysed rearrangement of dienyl acetates OAc Scheme 2. Mechanism (ref. 2) for the Pdo-catalysed rearrangement of dienyl acetates We now report the application of the Pd"-catalysed re-arrangement to substrates of greater complexity and show how it can be applied to the syntheses of the natural products (lOE,12Z)-9-hydroxyoctadeca- 10,12-dienoic acid r-dimorph- ecolic acid (2d); as its methyl ester, (2e)and (2E,4Z)-deca-2,4- dienal (2f).The syntheses of compounds (2e) and (2f)also incorporate useful Pd"-catalysed rearrangements of allylicacetate^.^ Full experimental details for all our Pdo- and Pd"- catalysed reactions are given herein.2062 J. CHEM. SOC. PERKIN TRANS. I 1988 Results and Discussion Further Pd-Catalysed Rearrangements of 3-Acetoxy- 1,4- dienes.-It was shown that (E)-3-acetoxyhexa-174-diene(Id) undergoes Pd"-catalysed rearrangement to give almost ex-clusively (E)-2-acetoxyhexa-3,5-diene(2g), whereas the Pdo- assisted rearrangement yields mainly (2E74E)- 1-acetoxyhexa-2,4-diene.Treatment of (Z)-3-acetoxyhexa- 1,4-diene with PdO catalyst also gave mainly (2E74E)- l-acetoxyhexa-2,4-diene,but Pd" catalyst gave a very slow reaction (48 h, room temperature) resulting in (E)-2-acetoxyhexa-3,5-diene(60), (2E74E)-1 -a~etoxyhexa-2~4-diene(30), and (2E74Z)-1-acetoxyhexa-2,4-amp;R2 a; R' b; R' = R2 = Me, R3 = H = Bu, R2 = Me, R3 = H c; R' = Me, R2 = Bu, R3 = H R' OAc d; R' = R3 = H, R2 = Me e; R2 = R3 = Me, R' = H (1) f; R' = MeCHzCHCH,, R2 = Me, R3 = H a; R' = Me, R2 = CHOAcMe b; R' = Bu, R2 = CHOAcMe c; R' = Me, R2 = CHOAcBupARZ d; R' = C5Hll, R2 = CHOH(CH,),CO,H R' e; R' = C,Hll, R2 = CHOH(CH,),CO,Me f; R' = C5Hl,, R2 = CHO (2) g; R' = H, R2 = CHOAcMe h R' = MeCHzCHCH,, R2 = CHOAcMe i; R' = C5H,,, R2 = CHOAc(CH,),CO,Me diene (10).Thus, the order of reactivity of double bonds in the Pd"-catalysed rearrangement is E-disubstituted Z-disub-stituted -vinyl.It was therefore of interest to examine a substrate containing an x-methylvinyl group and either an E-or 2-disubstituted double bond. We found that Pd"-catalysed rearrangement of (E)-3-acetoxy-2-methylhexa-174-diene (le) was rapid and gave predominantly (E)-2-acetoxy-5-methylhexa-3,5-diene. However, (Z)-3-acetoxy-2-methylhexa-1,4-diene re- acted very slowly (48 h, room temperature) to give the same product as the E-isomer. This result shows that the X-methylvinyl group does not participate readily in Pd"-catalysed rearrangements. The examples described make easily available a range of product dienes suitable for use in the Diels-Alder reaction.This extension of the chemistry described is under investigation. For certain applications of the Pd"-catalysed rearrangement in the synthesis of natural products, it was important to show that a 2-double bond, in 'skipped' relationship to the 2-double bond of a (1 E,42)-3-acetoxyhexa-1,4-diene7 does not interfere. Therefore (2E,52,8Z)-4-acetoxydeca-2,5,8-triene(1 f) was syn- thesised and exposed to Pd"-catalyst, and gave predominantly (3E,5Z,8Z)-2-acetoxydeca-3,5,8-triene(2h). In contrast, PdO- catalysed rearrangement gave 80 (3E,SE$Z)-2-acetoxy-deca- 333- triene. Pd- Cutalysed Ally lic Rearrangemen ts.-For the synthesis of (2E74Z)-deca-2,4-dienal(2f), see below we required a mono- ester of (E)-but-a-ene- 1,4-diol as starting material.We origin- ally prepared two such esters (3a) and (3b)l by saponification of the diacetate (3c) and dipivalate (3d) of the diol. These esters were conveniently prepared in high yield by Pdo-catalysed rearrangement of the corresponding diesters of (Z)-but-2-ene- 1,4-diol, a cheap commercially available compound. The mechanisms of these reactions presumably involve an initial Pdo-catalysed rearrangement to the diester of but-1-ene-3,4-diol, followed by a further Pdo-catalysed rearrangement to the observed product. R'OCH2CHHCH,0R2 (3a) R' = H, R2 = AC (3b) R' = H, R2 = Bu'CO (3~)R' = Ac, RZ = AC (3d) R' = Bu'CO, R2 = Bu'CO (3e) R' = Bu'SiMe,, R2 = Ac (3f) R' = Bu'SiMe,, R2 = H CH,=CHCHOR'CH,0R2 (4a) R' = H, R2 = Bu'SiMe, (4b) R' = Ac, R2 = Bu'SiMe, Bu'SiMe,OCH,CHHCHO (5) In a better approach, but-l-ene-3,4-diol was dimethyl-t- butylsilylated5 to give the silyl ether (4a) 92, which was converted into its acetate (4b) 94.In the presence of a catalytic quantity (5 mol) of PdCl,(MeCN), in benzene, the acetate (4b) gave the (E)-allylic acetate (3e) ratio of (3e): (4b) = 1.3: 1 after 2 h at room temperature. Treatment of the mixture of acetates with lithium aluminium hydride in ether, followed by chromatography, gave the (E)-allylic alcohol (3f) (54). Oxidation of the alcohol (3f) with pyridinium dichromate (1.5 mol equiv.) in dichloromethane afforded the (E)-aldehyde (5) (60).Pd"-Catalysed isomerisation of a (2)-allylic acetate into an (E)-allylic acetate should be a general reaction. For the synthesis of methyl x-dimorphecolate (see below) we needed to convert an aldehyde into an homologous x,P-unsaturated aldehyde. Although several methods have been reported for accomplishing this transformation, we have applied the Pd"-catalysed rearrangement of allylic acetates to the solution of this problem. The protocol shown in Scheme 3 was defined using 3-chlorobenzaldehyde as starting material, which was converted into (E)-3-chlorocinnamaldehyde(overall yield 230/amp; not optimised). Although this sequence requires five steps, most, if not all of these steps are trivial, simple reactions, and it is possible to proceed quickly from start to finish with minimal purification of intermediates.RCHO SRCHHCHO Scheme 3. Procedure for conversion of aldehydes into homologous x,P-unsaturated aldehydes. Reuganrs: i, CH,=CHMgBr, THF; ii, Ac20, DMAP (cat.), py; iii, PdCl,(MeCN), (cat.), benzene; iv, NaOMe (cat.), MeOH; v, MnO,, THF = tetrahydrofuran, DMAP = 4-dimethylaminopyridine. py = pyridine Sjwthesis of' Metjiyl sr-Dimorphecolate (2e).-The acid (2d) was originally obtained from marigold seeds (Calendula oflci-nulis L).' It has been isolated as its cholesteryl ester from human atheroma plaques' and recently was identified as a self-defensive substance of the rice plant Ory-a satiue L.9 A 10-step synthesis of methyl X-dimorphecolate (2e) from (E)-pent-2-en-4- yn-1-01, using a Lindlar reduction to generate the Z-double bond, has been reported.* However, the stereochemical homogeneity of the product was not confirmed. Our synthesis of ester (2e), based on the Pd"-catalysed rearrangement of acetoxydienes (cJ Equation l), is summarised in Scheme 4. Thus, the aldehyde (6),prepared by ozonolysis of methyl (92) octadec-9-enoate7 was treated with vinylmagnesium bromide in tetrahydrofuran to give the alcohol (7a) (61), which was converted into the acetate (7b) (60). In the presence of a catalytic quantity (5mol o/J of PdCl,(MeCN), the acetate (7b) C0.1~in benzene was equilibrated with the (E)-allylic acetate (8a) ratio of (7b):(8a) = 1 :3 after 45 min at room temperature.Treatment of the mixture with catalytic sodium methoxide in methanol gave the (a-allylic alcohol (8b) (64) J. CHEM. SOC PERKIN TRANS. I 1988 OR Me02C -CHo (6) (7b) R =Ac Ill Me02C4CHO Me02C4OR OR Me02C Z Scheme 4. Synthesis of (k)-methyl x-dimorphecolate. Reagents: i, CH,=CHMgBr, THF; ii, Ac,O, DMAP (catalytic), py; iii, ( MeCN),PdCl, (catalytic), C,H,; iv, NaOMe (catalytic), MeOH; v, MnO,, petroleum; vi, C,H, ,CHgCHMgBr, THF. THF = tetrahydrofuran; DMAP = 4-dimethylaminopyridine; py = pyridine and the secondary alcohol (7a) (17), after separation by PdCI,(MeCN), (5 mol ) in benzene (45 min, room chromatography on silica gel elution with petroleum-diethyl temperature) preferentially at the E-double bond to give ether (5:l).The alcohol (8b) in petroleum was oxidised with predominantly the (E,Z)-diene (29 (total yield of conjugated manganese dioxide (10 mass equiv.) to give the (E)-enal (9) dienes 95). Methanolysis of the diene (2i)gave methyl (74). 9-hydroxyoctadeca- 10,12-dienoate (2e) 74x1, after purifi-Coupling of the aldehyde (9)with (2)-hept- I-enylmagnesium cation by silica gel chromatography elution with petroleum- bromide prepared from (2)-1-bromoheptene, obtained from diethyl ether (3: l). The 'H and 13C n.m.r. spectra of the ester hexanal analogously to (2)-1-bromohexene from pentanal '1 obtained were in close agreement with the reported data for gave the dienyl alcohol (10a) (33) and recovered aldehyde (9) the (10E,12Z)-methyl ester (2e) prepared from natural CC-(36), after chromatography on silica gel elution with petrol- dimorphecolic acid (Zd).' ' However, minor resonances eum-diethyl ether (5:l).The alcohol (10a) was predominantly indicated the presence of ca. 15 E,E-isomer(s). This was ( 90) the (9E712Z)-isomer according to 'H and 3C n.m.r. expected because the Pd"-catalysed rearrangement of (1,542)-spectroscopic analysis. The dienyl acetate (lob), prepared from 3-acetoxy- 1,4-dienes is a kinetically controlled process favouring the alcohol (10a) in 78 yield, was isomerised in the presence of migration of the acetate via the E-double bond by a rate factor Z E ORz OR2 Scheme 5. Rerigcvm: i, C,H ,CHfCHMgBr, THF; ii, Ac,O, DMAP (catalytic), py; iii, PdCl,(MeCN), (catalytic), benzene; iv, NaOMe (catalytic), MeOH; v, Bu,N+F--.THF; vi, NaIO,, THF-pH 7 aq. phosphate buffer of ca. 5: 1 over migration via the 2-double bond (but see below).' Synthesis qf (2E,42)-Deca-2,4-dienaf (2f).-This compound is a flavour constituent of black tea.12 It has been synthesized from prop-2-yn- 1-01 using Wittig chemistry ' and from 3- dimethylaminopropenal by an application of the Benary reaction.', Our synthesis is summarised in Scheme 5. Thus, coupling of the aldehyde (5) with (2)-hept- 1-enylmagnesium bromide in tetrahydrofuran gave the (E,Z)-dienyl alcohol (lla) (78) that was acetylated to (llb) (87). These substances were contaminated with ca. 10 of conjugated dienes. Isomerisation of the acetate (llb) occurred with catalytic (5 mol ) PdCI,(MeCN), in benzene, but was significantly slower (ca.6 h for completion) than normal.1*2The product (94) was a 3 :1 mixture of the (E,Z)-dienyl acetate (12a) and an E,E-isomer. We rationalise these observations as being due to the deactivation of the E-double bond by the neighbouring silyloxy group (either by inductive electron withdrawal or by n+o* hyperconjuga-tion), making reaction at the 2-double bond competitive with reaction at the E-double bond. Methanolysis of the mixture of (12a) and its isomer, followed by desilylation, gave the diol(12b) after chromatography. Periodate cleavage of the diol (12b) in tetrahydrofuran-pH 7 phosphate buffer gave (2E,4Z)-deca- 2,4-dienal (2f), 15 overall from (12a), the spectroscopic properties of which were identical with those reported.', The chemistry described illustrates further uses of palladium in organic synthesis (for reviews see ref.16). Extension of this chemistry to the synthesis of leukotrienes and other hydroxy- polyunsaturated fatty acids is being investigated. Experimental Materials and Methods.-Dry solvents referred to below were prepared as follows: pyridine was kept over potassium hy- droxide, distilled and stored over molecular sieves (type 4A). Tetrahydrofuran and diethyl ether were stored over lithium aluminium hydride and immediately prior to use, distilled. Benzene was purified by successively washing with concentrated sulphuric acid, dilute sodium hydroxide, and water, followed by distillation from phosphorus pentaoxide under nitrogen.Deuteriobenzene was stored over molecular sieves (type 3A). Petroleum refers to light petroleum (b.p. 4amp;60 "C). T.1.c. was performed on Schleicher and Schull plastic sheets coated with silica gel (F 1500 LS 254); the plates were initially examined under U.V. light and spots were then visualised with potassium permanganate. Column chromatography was effec- ted under pressure, using Merck Kieselgel H (type 60). Evaporations were carried out using a rotary evaporator. M.p.s were determined using a Kofler hot-stage apparatus and are uncorrected. 1.r. spectra were recorded using either a Nicolet 20SXB or a Perkin-Elmer 257 spectrophotometer.Either a Unicam SP 800 spectrometer or a Cecil CE505 was employed to determine U.V. spectra. 'H N.m.r. spectra were measured using tetramethylsilane as internal standard. The spectra were determined at 200, 220, or 300 MHz using a Bruker WP 200, Perkin-Elmer R34 or Bruker WM 300 instrument, respectively. Mass spectra were determined using either a Kratos MS 9 or a Kratos MS 80 instrument. (E)-and (2)-Hexa- 1,4-dien-3-01, (E)-and (Z)-2-methylhexa- 1,4-dien-3-01, and (E,E)-,(E,Z)-,and (Z,Z)-hepta-2,5-dien-4- 01 were prepared by a literature proced~re,~." and were converted into the corresponding acetates by acetic anhydride- pyridine. All of these acetates gave 'H n.m.r. spectral data consistent with their assigned structures. Example of a Pd"-Catafysed Rearrangement: (E)-2-Acetoxy- hexa-3,5-diene.-To a stirred solution of (E)-3-acetoxyhexa- 1,4- J.CHEM. SOC. PERKIN TRANS. I 1988 diene (0.4 g, 2.86 mmol) in dry tetrahydrofuran (5 cm') was added PdCI,(MeCN), (0.037 g, 5 mol ) and the reaction was allowed to proceed for 10 min. The solvent was removed and pentane was added to the residue. Filtration and evaporation gave a liquid that was distilled (Kugelrohr) to afford (E)-2- acetoxyhexa-3,5-diene (0.36 g, 90), b.p. 36--38 "C at 4 mmHg: h,,,,,,(EtOH) 221 nm (E 26 000 dm3 mol-' cm-'); 6,(220 MHz; CCI,) 1.30 (3 H, d, J6.5 Hz, 1-Me), 1.98 (3 H, s, COMe), 5.08 (1 H, d, J 10.5 Hz, 6-H), 5.20 (1 H, d, J 17 Hz, 6-H), 5.30 (1 H, m, 2- H), 5.61 (1 H, dd, J 6.5 and 15 Hz, 3-H), and 6.21 (2 H, m, 4- and 5-H); m/z 140 (M'), 98 (M+ -42), and 43 (base peak).(E)-2-Acetox~~-5-methyfhexa-3,5-diene.-Asolution of the (E)-3-acetoxy-2-methylhexa-1,4-diene was treated as described above to give, after distillation (E)-2-acetoxy-5-methylhexa-3,5-diene (9373, b.p. 95-100deg;C at 20 mmHg: 6,(220 MHz, CDCI,) 1.34 (3 H, d, J 6.5 Hz, 1-Me), 1.84 (3 H, s, 5-Me), 2.05 (3 H, s, COMe), 5.00 (2 H, s, 6-H2), 5.43 (1 H, pentuplet, 2-H), 5.63 (1 H, dd, J6.6 and 16 Hz, 3-H), and 6.32 (1 H, d, J 16 Hz, 4-H); m/z 154 (M+), 112 (M' -42), 111 (M+ -43), 79 (M+ -75), and 43 (base peak). (3E,5Z,8Z)-2-Aceto.~ydeca-3,5,8-triene.-Asolution of (2E,- 52,82)-4-acetoxydeca-2,5,8-triene(0.3 g, 1.55 mmol) was treated as described above to give after distillation (3E,52,8Z)- 2-acetoxydeca-3,5,8-triene(0.279 g, 9373, b.p.96-98 "C at 0.05 mmHg: A,,,,,. 235 nm (E 19 400 dm3 mol-' cm-'); 6,(220 MHz, CCl,) 1.32 (3 H, d, J6.6 Hz, 1-Me), 1.66 (3 H, d, J6.6 Hz, 10- Me), 2.04 (3 H, s, COMe), 2.94 (2 H, t, 7-CH2), 5.3-5.6 (3 H, m, 2-, ,and 9-H), 5.66(1 H,dd, J7and 15 Hz, 3-H), 5.97(1 H, t, J 10 Hz, 5-H), and 6.55 (1 H, dd, J 11 and 15 Hz, 4-H); m/z 194 (M+),79 (M' -115), and 43 (base peak). (E)-1,4-Dipiuafoyfoxybut-2-ene(3d).-To an ice-cooled solu- tion of (Z)-but-2-ene-l,4-diol (26.4 g, 0.3 mol) in dry pyridine (200 cm3) was added trimethylacetyl chloride (81 cm3, 0.66 mol). After 3 h the solution was extracted with diethyl ether, and the extract washed with 5M hydrochloric acid and aqueous sodium hydrogen carbonate, dried, and evaporated to give (2)-1,4-dipivaloyloxybut-2-ene(74 g, 96).The crude dipivalate (12 g, 0.047 mol) in dry benzene (50 cm3) was treated with Pd(Ph,P), (1.1 g, 2 mol ) under nitrogen. The reaction was allowed to proceed for 4 h at room temperature. The solvent was removed and the residue was washed with petroleum through Celite. The combined filtrates were washed with 2 aqueous sodium cyanide and water, and the solvent was removed to give the title compound (11.8 g, 98); vmax.(liq. film) 2 974 and 1733 cm-'; 6,(200 MHz, CDCI,) 1.39 (18 H, s, Me3C), 4.58 (4 H, dd, J 1.5 and 4 Hz, 2 x CH,), and 5.79 (2 H, m, CH:CH); m/z 256 (M+),241 (M' -CH,), 155 (A4 -C5H902),85 (CsHgO), and 57 (base peak, C,H,'). (E)-1,4-Diacetoxybut-2-ene (3c).-To an ice-cooled solution of (Z)-but-2-ene-l,4-diol (17.8 g, 0.2 mol) in dry pyridine (100 cm3) was added acetic anhydride (42 cm3, 0.44 mol).After 6 h the solution was extracted with diethyl ether, and the extract washed with 5~ hydrochloric acid and aqueous sodium hydrogen carbonate, dried, and evaporated to give (2)-1,4- diacetoxybut-2-ene (28.8 g, 84). To a stirred solution of the crude diacetate (17.2 g, 0.1 mol) in dry benzene (75 cm3) was added Pd(Ph,P), (2.3 g, 2 rnol ). The reaction was allowed to proceed for 5 h at room temperature after which the solvent was removed and the residue washed with petroleum through Celite. The combined filtrates were washed with 2 aqueous sodium cyanide, dried, and evaporated to give the title compound (17 g, 98); 6,(200 MHz, C,D,) 1.89 (6 H, s, 2 x COCH,), 4.58 (4 H, dd, J 1.5 and 4.4 Hz, 2 x CH,), and 5.77-5.82 (2 H, m, CH:CH).J. CHEM. SOC. PERKIN TRANS. I 1988 3-Acetoxy-4-dimethyl-t-but-vlsilyloxybut-1 -ene (4b).-A solu-tion of but-1-ene-3,4-dio14 (4.4 g, 50 mmol) in dry N,N-dimethylformamide (30 cm3) was treated with imidazole (4.93 g, 72.5 mmol) followed by dimethyl-t-butylsilyl chloride (7.6 g, 50 mmol) for 4 h at room temperature. The solution was poured into brine and extracted with diethyl ether. The extract was washed with dilute hydrochloric acid, dried, and evaporated to give the crude product (4a) (9.3 g, 92). This was dissolved in dry pyridine (30 cm3) and treated with acetic anhydride (5.6 cm3, 60 mmol) followed by 4-dimethylaminopyridine (0.28 g, 5 mol z)for 1 h at room temperature.The solution was washed with 5111 hydrochloric acid and extracted with diethyl ether. The extract was washed with aqueous sodium hydrogen carbonate and water, dried, and evaporated to provide a residue which by chromatography on silica gel with petroleum-diethyl ether (9:1) as eluant yielded the title compound (4b) (1 1.43 g, 94); v,,,,(CHCl,) 2 930 and 1 750 cm-'; 6H(200 MHz, CDC1,) 0.06 (6 H, s, SiMe,), 0.89 (9 H, s, CMe,), 2.09 (3 H, s, COMe), 3.67 (2 H, d, J 5 Hz. 4-CH2), 5.19-5.35 (3 H, m, 2 x 1- and 3-H), and 5.82 (1 H, ddd, J6,ll and 15 Hz, 2-H); m/z 187 (M+ -57) and 43 (base peak) (Found: M+ -57, 187.0795.C,H,,O,Si requires 187.0795). (E)-1-Dimethy/-t-butylsilyfoxybut-2-en-4-of (3f).-A stirred solution of the acetate (4b) (1 1.39 g, 46.6 mmol) in dry benzene (70 cm3) was treated with PdCl,(MeCN) (0.543 g, 5 rnol ). The reaction was allowed to proceed for 2 h at room temperature after which the solvent was removed and the residue extracted with petroleum and the extract filtered through Celite. The combined filtrates were washed with 2 aqueous sodium cyanide and water, dried, and evaporated to give a ca. 1.3 : 1 mixture of acetates (3e)and (4b) (10.95 g, 96). To a cooled solution of the crude mixture (7.5 g, 31 mmol) in dry diethyl ether (I80 cm3) was added lithium aluminium hydride (0.582 g, 15 mmol). After 2 h at room temperature, the mixture was cautiously added to ice-cooled 5111 hydrochloric acid and extracted into diethyl ether.The extract was washed with water, dried, and evaporated to provide a residue which by chroma- tography on silica gel with petroleumdiethyl ether (5: 1) as eluant gave two products. The faster-running component was the acetate (4b) (1.34 g, 18). The slower-running component was the alcohol (3f) (3.4 g, 54); v,,,~(CHCl,) 3 350,2 930, and 2 858 cm-'; 6,(200 MHz, CDCl,) 0.036 (6 H, s, SiMe,), 0.86 (9 H, s, CMe,), 3.72 (1 H, br s, OH), 4.04-4.09 (2 H, m, 1-CH,), 4.134.1 5 (2 H, m, 4-CH2), and 5.76-5.79 (2 H, m, 2- and 3- H) (addition of D,O caused the signal at 6 3.72 to disappear); m/z 202 (M'), 171 (M+-31), 145 (M+ -57), and 127 (M' -75) (Found: M+, 202.1381.CloH,,O,Si requires 202.1389). (E)-4-Dimt.th~~l-t-butylsilylo.uybut-2-enul vigorously(5).-A stirred solution of the alcohol (3f) (4.5 g, 22 mmol) in dry dichloromethane (35 cm3) was oxidised with pyridinium dichromate (12.4 g, 33 mmol) for 5 h at room temperature. The mixture was filtered through silica gel and the silica was washed with diethyl ether. The combined extracts were washed with dilute hydrochloric acid, dried, and evaporated to afford a residue which by chromatography on silica gel with petroleum- diethyl ether (5:1) as eluant gave the aldehyde (5) (2.62 g, 60); v,,,,(CHCl,) 2 960, 2 930, and 2 860, and 1 690 cm-'; amp;(200 MHz, CDCl,) 0.095 (6 H, s, SiMe,), 0.93 (9 H, s, CMe,), 4.45 (2 H, dd, J 2 and 4 Hz, 4-CH2), 6.44 (1 H, d, J 8 and 16 Hz, 2-H), 6.89 (1 H, dt, J 4 and 16 Hz, 3-H), and 9.60 (1 H, d, J 8 Hz, CHO): 6, 193.0, 156.2, 130.8, 62.4, 25.9, 25.7, and 5.32; m/z 200 (M+)and 143 (M+ -57) (Found: M+,200.1219.C,,H,,O,Si requires 200.1233). (E)-3-Ch/orocznnumafde~yde.-A solution of 3-chloro-benzaldehyde (1.40 g, 0.01 mol) in dry tetrahydrofuran (10 cm3) was treated with vinylmagnesium bromide (0.01 1 mol) in dry tetrahydrofuran (10 cm3). After 40 min at room temperature the solution was quenched with saturated aqueous ammonium chloride and extracted with diethyl ether (2 x 20 cm3). The combined extracts were washed with aqueous sodium hydrogen carbonate and water, dried, and evaporated to give the crude alcohol (0.942 g, 56).A solution of the alcohol (0.942 g) in pyridine (4 cm3) was treated with acetic anhydride (0.635 cm', 6.7 mmol) followed by 4-dimethylaminopyridine (0.032 g, 5 mol ). After 1 h at room temperature the mixture was poured into dilute hydrochloric acid and extracted into diethyl ether. The extract was washed with aqueous sodium hydrogen carbonate and water, dried, and evaporated to give the acetate (0.968 g, 82). The acetate (0.768 g) was treated with PdCl,(MeCN), (40 mg, 5 mol ) in benzene (6 cm3) and the resulting mixture was heated at 80deg;C for 1 h. After cooling, the solvent was removed and the residue extracted with petroleum. After filtration through Celite the petroleum extract was washed with 2 aqueous sodium cyanide, dried, and evaporated to give 3-acetoxy-1-m-chlorophenylpropene (0.76 g).The crude acetate (0.6 g, 2.84 mmol) in dry methanol (2 cm3) was treated with sodium methoxide in methanol (0.042 cm3, 5 mol NaOMe) under nitrogen for 1 h at room temperature. The mixture was treated with IR-120Hf resin until neutral, filtered, and the filtrate evaporated. Chromatography of the residue on silica gel with petroleum-diethyl ether (2: 1) as eluant gave (E)-3- chlorocinnamyl alcohol (0.4 g, 83). To a vigorously stirred solution of the (E)-alcohol(O.168 g, 0.1 mmol) in petroleum (10 cm3) was added manganese dioxide (1.68 g, 10 mass equiv.). After 3 h at room temperature the mixture was filtered through Celite and the filter pad was washed with diethyl ether.The combined filtrates were concentrated to give a crude product which was recrystallised from ethanol to afford (E)-3-chlorocinnamaldehyde (0.1g, 61), m.p. 7 1-73 "C; vmax,(KBr) 1 677 and 1 690 cm-'; 6,(300 MHz, CDCl,) 6.46 (1 H, d, J 16 Hz, 3-H), 6.73 (1 H, dd, J 8 and 16 Hz, 2-H), 7.32-7.75 (4 H, m, ArH), and 9.72 (1 H, d, J 8 Hz, CHO); m/z 166 (M+)and 137 (Mf -CHO) (Found: M+,166.0178. C9H,3sC10 requires 166.01 85). Methyl 9-Hydroxyundec- 10-enoate (7a).-To a stirred ice- cooled solution of the aldehyde (6)'' (8.1 13 g, 44 mmol) in dry THF (50 cm3) was added vinylmagnesium bromide (6.84 g, 52 mmol) in dry THF (30 cm3). After 20 min at 0 OC, the solution was quenched with saturated aqueous ammonium chloride and extracted with diethyl ether.The extract was washed with aqueous sodium hydrogen carbonate and water, dried, and evaporated to give the title compound (7a) as a syrup (5.69 g, 61); v,,,.(CHCl,) 3 500,2 931, and 1 740 cm-'; 6H(200 MHz, CDCl,) 1.21-1.73 (12 H, m, 6 x CH,), 1.81 (1 H, br s, OH), 2.31 (2 H, t, J7 Hz, 2-H,), 3.67 (3 H, s, CO,Me),4.08 (1 H,dt, J6 and 6 Hz, 9-H), 5.12 (1 H, dt, J 1, 1, and 10 Hz, 11-H), 5.26 (1 H, dt, J 1, 1, and 17 Hz, 11-H), and 5.82 (1 H, ddd,J6, 10,and 17 Hz, 10-H) (addition of D,O caused the signal at 6 1.81 to disappear); m/z 187 (Mf -27) and 155 (M+ -59). Methyl 9-Acetoxyundec-10-enoate(7b).-To a solution of the alcohol (7a) (4.28 g, 20 mmol) in pyridine (25 cm3) was added acetic anhydride (2.2 cm3, 24 mmol) followed by 4-dimethyl- aminopyridine (0.1 12 g, 5 mol ).After 1 h at room temperature the solution was poured into dilute hydrochloric acid and extracted with diethyl ether. The extract was washed with aqueous sodium hydrogen carbonate and water, dried, and evaporated to afford a residue which by chromatography on silica gel with petroleumdiethyl ether (2: 1) as eluant gave the title compound (7b) as a syrup (2.99 g, 60); v,,,,(CHCI,) 2 930, 2 860, and 1 740 cm-'; 6H(200 MHz, CDCl,) 1.26-1.50 (8 H, m, 4 x CH,), 1.61-1.73 (4 H, m, 2 x CH,), 2.06 (3 H, s, COMe), J. CHEM. SOC. PERKIN TRANS. I 1988 2.30 (2 H, t, J7 Hz, 2-CH2), 3.67 (3 H, s, CO,Me), 5.13-5.23 (3 H, m, 2 x 11- and 9-H), and 5.77 (1 H, ddd, J6,10, and 17 Hz, 10-H); mlz 214 (M+ -42) and 43 (base peak, C2H30+).Methyl (E)- 1 1 -Hydroxyundec-9-enoate (8b).-To a stirred solution of the acetate (7b) (2.72 g, 11 mmol) in dry benzene (15 cm3) was added PdCl,(MeCN), (0.12 g, 5 mol ). The reaction was allowed to proceed for 45 min at room temperature after which the solvent was removed and the residue extracted with petroleum and the extract filtered through Celite. The filtrate was washed with 2 aqueous sodium cyanide (x 3), dried, and evaporated to give a 1 :3 mixture of the acetates (7b) and (8a). The syrup (2.5 g, 11.7 mmol) in dry methanol (18 cm3) was treated with sodium methoxide (0.257 g, 5 mol NaOMe) under nitrogen for 6 h at room temperature. The solution was treated with IR-120H+ until neutral, filtered, and the filtrate evaporated to afford a residue which by chromatography on silica gel with petroleum-diethyl ether (5:1) as eluant gave two fractions.The fast-running component was the alcohol (7a) (0.394 g, 17). The slower-running component was methyl (9E)- 1 1-hydroxyundec-9-enoate (8b) (1.6 g, 64); v,,,,(CHCI,) 3 500,2 930,2 860, and 1 740 cm-'; 6H(200 MHz, CDCl,) 1.3 1- 1.47(8 H, m, 4 x CH,), 1.49 (1 H, br s, OH), 1.54-1.65 (2 H, m, CH,), 2.05 (2 H, m, 8-CH2), 2.31 (2 H, t, J7 Hz, 2-CH2), 3.67 (3 H, s,CO,Me), 4.09 (2 H, dd, J 1 and 5 Hz, 11-H), and 5.55-5.69 (2 H, m, 9- and 10-H) (addition of D,O caused the signal at 61.49 to disappear); mjz 196 (M' -18). Methyl (9E)-1 1-Oxoundec-9-enoate (!)).-To a rapidly stirred solution of the alcohol (8b) (1.6 g, 7.5 mmol) in petroleum (40 cm3) was added manganese dioxide (16 g, 10 mass equiv.). After 18 h at room temperature the mixture was filtered through Celite and the filter pad was washed with diethyl ether ( x 2).The combined eluants were evaporated to afford a residue, chromatography of which on silica gel with petroleum-diethyl ether (2: 1) as eluant gave the aldehyde (9) (1.17 g, 74): v,,,~(CHCl,) 2 930, 1 738, and 1 695 cm-I; 6,(200 MHz, CDC1,) 1.33-1.66 (12 H,m, 6 x CH,), 2.31 (2 H, t, J8 Hz, 2-CH2), 3.67 (3 H, s, CO,Me), 6.17 (1 H, dd, J8 and 16 Hz,10-H),6.86(1H,dt,J7and16Hz,9-H),and9.51(1H,d,J8 Hz,CHO);m/z212(Mf), 181 (M' -31), 152(M+ -60),and 55 (base peak) (Found: M', 212.1406. C12H2,03 requires 21 2.141 2).Methyl (9E,12Z)- 1 l-Hydro.~yoctadecu-9,12-dienoate(lOa).-To a flame-dried flask under argon containing magnesium (0.108 g, 4.5 mmol) in dry tetrahydrofuran (8 cm3) was added 1,2-dibromoethane (4 drops) followed by (Z)-1 -bromoheptene (0.531 g, 3 mmol) in dry tetrahydrofuran (8 cm3). The mixture was heated under reflux for 6 h. After the mixture had cooled to room temperature a solution of the aldehyde (9) (0.424 g, 2 mmol) in tetrahydrofuran (8 cm3) was added and the mixture stirred for a further 8 h. The mixture was quenched with saturated aqueous ammonium chloride and extracted with diethyl ether. The extract was washed with brine, dried, and evaporated to afford a residue, chromatography of which on silica gel with petroleum-diethyl ether (5:1) as eluant gave successively the (Z)-1-bromoheptene (0.236 g), aldehyde (9) (0.153 g, 36), the title compound (10a) (0.206 g, 33); v,,,.(CHCI,) 3 520, 2 930, 2 855, 1 740, and 1 690 cm-'; 6H(200 MHZ, C6D6) 0.96 (3 H, t, 18-Me), 1.24 (16 H, m, 8 x CH,), 1.56 (3 H, m, CH, and OH), 2.02 (2 H, m, 14-CH2), 2.14 (2 H, t, J 7 Hz, 2-CH2), 3.38 (3 H, s, CO,Me), 4.95 (1 H, m, 11-H), and 5.34-5.68 (4 H, m, 9-, lo-, 12-, and 13-H); 6, 173.4, 133.0, 132.6, 131.2, 130.9, 68.9, 50.9, 34.1, 32.5, 32.4, 31.8, 29.6, 29.5, 29.4, 29.3, 28.0, 25.3, 22.9, and 14.2; m/z 310 (M+), 292 (M' -18), and 43 (base peak) (Found: M+, 310.2493.C19H3403 requires 310.2508). Methyl (9E, 122)- 1 1 -Acetoxyoctadeca-9,12-dienoute(lob).-To a solution of the alcohol (10a) (0.206 g, 0.66 mmol) in pyridine (2 cm3) was added acetic anhydride (0.075 cm3, 0.79 mmol) followed by 4-dimethylaminopyridine (4 mg, 5 rnol ).After 30 min at room temperature the mixture was washed with dilute hydrochloric acid (1~) and extracted into diethyl ether. The extract was washed with saturated aqueous sodium hydro- gen carbonate and water, dried, and evaporated to afford a residue, chromatography of which on silica gel with petroleum- diethyl ether (2: 1) as eluant gave the dienyl acetate (lob) (0.182 g, 78); Vmax.(CHC13) 2 930, 2 860, and 1 740 Cm-'; 6H(200 MHz, CDCI,) 0.96 (3 H, t, 18-Me), 1.38 (16 H, m, 8 x CH,), 1.62 (2 H, m, CH,), 2.09 (3 H, s, COMe), 2.14 (2 H, m, 14-CH2), 2.29 (2 H, t, J7 Hz, 2-CH2), 3.67 (3 H, s, CO,Me), 5.30-5.78 (4 H, m), and 5.96 (1 H, dd, J 7 and 15 Hz, 10-H) (Found: M+, 352.2602.C, 1H3604 requires 352.2613). Pd"-Catalysed Rearrangemenr of Methyl (9E,122)-11-,4cet- o.~yoctadeca-9,12-dienoute(10b)-A solution of the dienyl acetate (lob) (0.150 g, 0.43 mmol) in dry benzene (2 cm3) was treated with PdCI,(MeCN), (5 mg, 5 rnol ). The reaction was allowed to proceed for 45 min at room temperature after which the solvent was removed and the residue extracted with petroleum. The extract was filtered through Celite and the combined filtrates were washed with 2 aqueous sodium cyanide, dried, and evaporated to give predominantly methyl (1OE,12Z)-9-acetoxyoctadeca-10,12-dienoate(2i) (0.145 g, 97); vmax.(CHC1,) 2 930, 2 860, and 1 740 cm-'; 6amp;00 MHz, CDCl,) 0.85 (3 H, t, 18-Me), 1.03-1.43 (14 H, m, 7 x CH,), 1.57-1.90 (4 H, m, 2 x CH,), 2.05 (3 H, s, COMe), 2.18 (2 H, d, J 7 Hz,14-CH,), 2.29 (2 H, t, J 8 Hz, 2-CH,), 3.63 (3 H, S, CO,Me), 5.23 (1 H, m, 9- or 13-H), 5.31 (1 H, m, 9- or 13-H), 5.51 (1 H,dd,J7and 15Hz, 10-H),5.94(1 H,t,J11 Hz, 12-H), and6.50(1 H,dd,Jll and 15Hz, ll-H);m/z352(M+)310(M+ -42) and 292 (M+ -60) (Found: M+,352.2602. C21H3604 requires M+,352.2613).Methjd (lOE, 12Z)-9-Hj~dro.~~ocrudeca-10,12-dienoate(2e).-A solution of the dienoate (2i) (0.145 g, 0.41 mmol) in dry methanol (1 cm3) was treated with sodium methoxide (5 mol "/, NaOMe) under nitrogen for 5 h at room temperature. The mixture was treated with IR-120H+ resin until neutral, filtered, and the filtrate evaporated to afford a residue, chroma- tography of which on silica gel with petroleum-diethyl ether (3:1) (containing 1 triethylamine) as eluant gave the title compound (2e) (0.094 g, 74); h,,,.(EtOH) 233 (E 23 480 dm3 mol-' cm-') and 244sh nm (14 490); v,,,~(CHCl,) 3 430, 2 930, 2 860, and 1 740 cm-I; 6,(200 MHz, CDCl,) 0.88 (3 H, t, 18-Me), 0.92-1.47 (14 H, m, 7 x CH,), 1.55-1.65 (3 H, m, CH, and OH), 2.18 (2 H, q, J7 Hz, 14-CH2), 2.30 (2 H, t, J 7 Hz, 2- CH,), 3.67 (3 H, s, CO,Me), 4.14 (1 H, dd, J6 and 13 Hz, 9-H), 5.46(1H,dt,J7andllHz,13-H),5.65(1H,dd,J7and15Hz, 10-H), 5.97 (1 H, t, J 11 Hz, 12-H), and 6.48 (1 H,dd, J 11 and 15 Hz, 11-H); 6, 174.2, 135.8, 133.0, 127.8, 125.9, 72.9, 51.4, 37.4, 34.1, 31.5, 29.3,29.2,29.1,27.8, 25.4,24.9,22.6, and 14.0; mi=310 (M+),292 (M+ -18), and 279 (M+ -31) (Found: M', 310.2487.C,9H3403 requires M+,310.2508). (2E,5Z)-1-Dinieth~l-t-hut~lsiI~~losj~undecu-2,5-dit.n-4-ol (lla).-A suspension of magnesium (0.432 g, 18 mmol) in dry tetrahydrofuran (30 cm3) under argon was treated with 1.2-dibromoethane (4 drops). The mixture was heated under reflux for 10 min after which (Z)-1-bromoheptene (3.19 g, 18 mmol) in tetrahydrofuran (10 cm3) was added and heating under reflux continued for 3.5 h. The mixture was cooled and a solution of the aldehyde (5) (2.1 g, 11 mmol) in tetrahydrofuran (10 cm3) was added. After the mixture had been stirred for a further 1 h at room temperature, the reaction was quenched with saturated J.CHEM. SOC. PERKIN TRANS. I 1988 aqueous ammonium chloride. The resulting mixture was extracted wiith diethyl ether and the combined extracts were dried and evaporated to provide, by chromatography on silica gel with petroleumdiethyl ether (5: 1) as eluant, the (E,Z)-dienyl alcohol (lla) (2.56 g, 78); v,,,~(CHCI,) 3 355, 2 957, 2 929, and 2 858 cm- '; 6,(200 MHz, CDCI,) 0.067 (6 H, s, SiMe,). 0.91 -0.99 (12 H, m, CMe, and ll-Me), 1.22-1.50 (6 H, m, 3 x CH,), 1.73 (1 H, br s, OH), 2.04-2.11 (2 H, m, 7- CH,), 4.17 (2 H, m, 1-CH,), 4.97 (1 H, m, 4-H), and 5.34-5.84 (4 H, m, 2-, 3-, 5-, and 6-H); 6, 132.6, 131.7, 130.9, 130.2, 68.4, 63.3, 31.6, 29.4, 27.8, 26.1, 25.8, 22.6, 18.5, 18.1, 14.1, -3.4, and -5.1; m,/z 298 (M'), 280 (Mi -18), and 241 (M+ -57) (Found: M +, 298.2323.C, 7H3402Si requires M', 298.2328). (2E,5Z)-4- Acetoxy- 1 -dimethyl-t-hutylsilyloxyundeca-2,5-diem (Ilb). -A solution of the dienol (lla) (2.4 g, 8 mmol) in dry pyridine ( 15 cm3) was treated with acetic anhydride (0.91 cm3, 9.7 mmol) followed by 4-dimethylaminopyridine (0.045 g, 5 mol "/J for 1 h at room temperature. The solution was poured into 5M hydrochloric acid and extracted into diethyl ether. The extract was washed with aqueous sodium hydrogen carbonate and water. dried, and the solvent removed to give the compound (Ilb) (2.36 g, 870,:)); v,,,~(CHCl,) 2 930 and 1 740 cm-'; 6,(200 MHz, CDCI,) 0.061 (6 H, s, SiMe,), 0.854.94 (12 H, m, CMe, and 11-Me), 1.22--1.64 (6 H, m, 3 x CH,), 2.05 (3 H, s,COMe), 2.09 (2 H, m.7-CH2),4.17 (2 H, m, 1-CH,), 5.38 (1 H, m), 5.52- 5.85 (3 H, m), and 6.02 (1 H, m); m/z 283 (M' -57), 281 (M' -59), and 43 (base peak) (Found: Mf -57, 283.1732. C,5H,,0,Si requires 283.1729). (3E,5Z)-2-.1ceto.vy-1-dirnethyl-t-butylsil~lo.xyundeca-3,5-diene (12a). A stirred solution of the diene (llb) (2.3 g, 6.9 mmo1)in dry benzene (5 cm3) was treated with PdCI,(MeCN), (0.087 g, 0.34 mmol). The reaction was allowed to proceed for 2 h at room temperature after which the solvent was removed and the residue extracted with petroleum. The extract was filtered through Celite and the combined filtrates were washed with 2":, aqueous sodium cyanide, dried, and evaporated to give predominantly the diene (12a) (2.16 g, 94); 6,(200 MHz, CDCI,) intrr ulici 0.06 (6 H, s, SiMe,), 0.89 (12 H, m, CMe, and 1 1-Me), 1.25 (6 H, m, 3 x CH,), 2.05 (3 H, s, COMe), 2.1 1 (2 H, m, 7-CH2).3.68 (2 H, m, 1-CH,), 5.36-5.89 (4 H, m, 2-, 3-, 5-, and 6-H). and 6.58 (1 H, dd, J 11 and 15 Hz, 4-H). (3E,5Z)-l/iz~ec.a-3,5-dzene-1,2-di~l(12b).-A solution of the diene (12a) (2.16 g, 6.3 mmol) in dry methanol (10 cm3) was treated with sodium methoxide in methanol (0.082 cm3, 5 mol NaOMe) under nitrogen for 12 h at room temperature. The mixture was treated with IR-120H' resin until neutral, filtered, and evaporated. The crude product (1.48 g) was dissolved in tetrahydrofuran (20cm3) and treated with tetrabutylammonium fluoride in tetrahydrofuran (5.95 cm3, 5.95 mmol F-) for 1 h at room temperature.The solution was poured into water, ex- tracted with diethyl ether, and the extract dried and evaporated to afford a residue, chromatography of which on silica gel with petroleum-diethy1 ether (5: 1) (containing 1 triethylamine) as eluant gave the diol(12b) (0.155g, 17); v,,,,(CHCI,) 3 380 and 2 930cm ': 6,(200 MHz, CDCI,), 0.89 (3 H, t, 11-Me), 1.89 (6 H, m, 3 x Cllz).2.13 (2 H, m, 7-CH2), 2.41 (2 H, br s, OH), 3.49 (1 H,dd,J7.5and 15Hz, l-H),3.66(1 H,dd,J3.5and15Hz,l-H), 4.24 (1 H, m. 2-H), 5.45 (1 H, dt, J7.5 and 16 Hz, 3-H), 5.58 (1 H, dt, J 6.5 and 11 Hz, 6-H), 5.98 (1 H, t, J 11 Hz, 5-H), and 6.60 (1 H, dd, J 11 and 16 Hz, 4-H) (addition of D,O caused the signal at 6 2.41 to disappear); rnjz 185 (MH+)and 167 (MHf -18) (Found: M', 184.1471.C,,H,,O, requires M+, 184.1463). (2E,4Z)-Deca-2,4-dienal (2f).-A solution of the diol (12b) (0.059 g, 0.32 mmol) in tetrahydrofuran (0.7 cm3) was treated with a solution of sodium periodate (0.075 g, 0.35 mmol) in pH 7 phosphate buffer (0.5 cm3) for 1 h at room temperature. The suspension was filtered, washed with water, and extracted with diethyl ether and the extract dried and evaporated. Chroma- tography of the residue on silica gel with petroleum-diethyl ether (5 :1) as eluant gave predominantly (2E,4Z)-deca-2,4- dienal (2f) (0.045 g, 82); v,,,~(CHCI,) 1 680 and 1 630 cm-'; 6,(200 MHz, CDCI,) inter alia 0.91 (3 H, m, 10-Me), 1.1 1-1.66 (6 H, m, 3 x CH,), 2.35 (2 H, m, 6-CH2), 6.04 (1 H, dt, J8 and 11 Hz, 5-H), 6.14 (1 H, dd, J 8 and 15 Hz, 2-H), 6.36 (1 H, dd, J 11 Hz,4-H),7.44(1 H,dd, J11 and 15Hz,3-H),and9.63(1 H,d, J 8 Hz, CHO); mjz 152 (M+),123 (Mi -29), 95 (M -57), and 81 (base peak) (Found: M+, 152.1204.C,,H,,O requires M, 152.1201). Acknowledgements We thank the S.E.R.C. for financial support and Professor L. Crombie for a sample of methyl a-dimorphecolate derived from the natural acid. References 1 B. T. Golding, C. Pierpoint, and R. Aneja, J. Chcwi. Soc., Chem. Commun., 1981, 1030. 2 E. H. Curzon, B. T. Golding, C. Pierpoint, and B. W. Waters, J. Organomet. Chem., 1984, 262, 263. 3 P. M. Henry, J. Am. Chem. Soc., 1972, 92, 5200. 4 D. A. Howes, M. H. Brookes, D. Coates, B. T. Golding, and A. T. Hudson, J. Chen?. Rex, 1983, (S),9; (M),217. 5 E. J. Corey and A. Venkateswarlu, J. Am. Chem. Soc., 1972,94,6190. 6 M. Julia and C. Lefebvre, Tetrahedron Lett., 1984, 189. 7 R. C. Badami and L. J. Morris, J. Am. OilChem. Soc ., 1965,42, 11 19. 8 C. J. W. Brooks, W. A. Harland, G. Steel, and J. D. Gilbert, Biochim. Biophys. Acta, 1970, 202, 563. 9 T. Kato, Y. Yamaguchi, T. Hirano, T. Yokoyama. T. Uyehara, T. Namai, S. Yamanaka, and N. Harada, Chem. Lett., 1984,409. 10 A. V. Rama Rao, E. Rajarathnam Reddy, G. V. M. Sharma, P. Yadagiri, and J. S. Yadav, Tetrahedron Letr., 1985. 465. 11 L. Crombie and S. J. Holloway, J. Chem.Soc., Cheni. Commun., 1984, 953. 12 W. Renold, R. Naf-Muller, U. Keller, B. Willhalm. and G. Oholff, Heiv. Chini. Acta, 1974, 57, 1301. 13 G. Rickards and L. Weiler, J. Org. Chem., 1978, 43. 3607. 14 F. Naf and R. Decorzant, Heir. Chin?. Acta, 1974, 57, 1309. 15 E. L. Jackson, in 'Organic Reactions,' ed. R. Adams, Wiley, New York, vol. 11, p. 341. 16 B. M. Trost, Acc. Chem. Res., 1980, 13, 385; E. I. Negishi, ihid.,1982, 15, 340; R. F. Heck, 'Palladium Reagents in Organic Synthesis,' Academic Press, London, 1985. 17 E. A. Braude and J. A. Coles, J. Chem. Soc., 1951. 2078 and 2085. 18 cf. B. S. Furniss, A. J. Hannaford, V. Rogers, P. W. G. Smith, and A. R. Tatchell, 'Vogel's Textbook of Practical Organic Chemistry,' Longman, London, 1978, p. 419. Received 1 lth May 1987; Paper 71824