J. CHEM. SOC. PERKIN TRANS. 1 1994 Synthesis of (2)-Homoallylic Alcohols and Homoprop-2-ynylic Alcohols via Palladium-catalysed Hydrogenolysis of Prop-2-ynylic Cyclic Carbonates Suk-Ku Kang," Dong-Chul Park, Dong-Gyu Cho, Jea-Uk Chung and Kyung-Yun Jung Department of Chemistry, Sung Kyun Kwan University, Natural Science Campus, Suwon 440-746, Korea The decarboxylation-hydrogenolysis of Bu",P afforded (Z)-moth Aphomia gularis has been synthesized. Optically active (2)-homoallylic and homoprop-2-ynylic alcohols are versatile chiral synthons in organic synthesis. In the literature, stereoselective synthesis of (2)-homoallylic alcohols by addition of crotylstannanes to aromatic aldehydes has been reported.' We report here a convenient one-pot synthetic method for the highly stereoselective preparation of (Z)-homoallylic alcohols 2 and homoprop-2-ynylic alcohols 3 utilizing palladium-catalysed selective hydrogen~lysis,~.~ details of which are shown in Scheme 1 and Table 1.2ii 1 a P = Bn, R = n-C5HI1 b P=MPM,R=Et 3 Scheme 1 Reagents and conditions: i, HC02NH, (4 equiv.), Pd(acac),-Bu",P (cat.), PhH, reflux; ii, HCO,NH, (1 equiv.), Pd(acac),-Bu",P (cat.), PhH, room temp. (MPM = p-methoxy-phenylmethyl) The internal prop-2-ynylic cyclic carbonate la reacted with 4 equiv. of ammonium formate in the presence of Pd(a~ac)~ (acac = acetylacetonate) and Bu",P as catalysts in benzene at reflux for 3 h to afford the (2)-homoallylic alcohol 2a in 76 yield, the structure of which was confirmed by 'H NMR (300 MHz) coupling constants of the olefinic protons (entry 1).It is presumed that Pd-catalysed decarboxylation-hydrogenolysis gives the homoprop-2-ynylic alcohol 3a as an intermediate (checked by TLC), which is subsequently reduced with excellent stereoselectivity ( >99) to the (Z)-homoallylic alcohol 2a by ammonium formate as a hydrogen donor in the presence of Pd- ~atalyst.~As indirect evidence for the intermediary of alcohol 3a, the reaction of the carbonate la with 1 equiv. of Pd(acac), and Bu",P afforded the homoprop-2-ynylic alcohol 3a in 93 yield (entry 2).? It is notable that under the same conditions, with benzene as solvent, stirring at room temperature afforded 3a in 97 yield (entry 3). This conversion was applied to the prop-2-ynylic cyclic carbonate lb and thus the (2)-homoallylic alcohol 2b and the homoprop-Zynylic alcohol 3b were obtained (entries 4 and 5).In contrast to the internal prop-2-ynylic cyclic carbonate, decarboxylation-hydrogenolysis of the terminal prop-Zynylic carbonate l~,~with 2 equiv. of ammonium formate in the presence of a catalytic amount of Pd(acac), and Bu",P tetrahydrofuran (THF) at reflux for 30 min, provided the prop-2-ynylic cyclic carbonates which have an internal acetylenic bond with ammonium formate in the presence of a catalytic amount of Pd(acac), and homoallylic alcohols or homoprop-2-ynylic alcohols depending on the reaction conditions, however, hydrogenolysis of terminal prop-2-ynylic cyclic carbonates gave homoallylic alcohols; using (Z)-homoallylic alcohol 2b as a chiral synthon, the male sex pheromone of the pyralid homoallylic alcohol 2c as the sole product (entry 6).$ Presumably, the allenic alcohol 4 and the homoprop-2-ynylic alcohol 3c are the intermediates.As indirect evidence for this, treatment of lc with 1 equiv. of ammonium formate in the presence of Pd(acac), and Bu",P in THF at reflux provided mixtures of the allenic alcohol 4 and the homoprop-2-ynylic alcohol 3c (Scheme 2; entry 7).$ It is notable that the reaction of 0. lc OH OH 3c Scheme 2 Reagents and conditions: i, HCO,NH, (1 equiv.), Pd- (acac),-Bu",P (cat.), THF, reflux, 30 min lc with 1 equiv. of ammonium formate in the presence of Pd(acac), and Bu",P in benzene at room temperature afforded the allenic alcohol 4 as the major product (entry 8).The results of the palladium-catalysed hydrogenolysis of prop-2-ynylic cyclic carbonates are summarized in Table 1.Using (2)-homoallylic alcohol 2b as a chiral synthon, the male sex pheromone of the pyralid moth Aphomia gularis 76 was synthesized (Scheme 3). The homoallylic alcohol 2b was protected as methoxymethyl (MOM) ether and then the p-methoxyphenylmethyl (MPM) protecting group was removed to furnish the alcohol 5, a;' -24 (c 0.46, CHC1,). The alcohol 5 was oxidized and Wittig olefination gave the a,P-unsaturated ester 6 (Z: E = 1.3 :1). The (2)-a,P-unsaturated ester 6 was subjected to deprotection, followed by lactonization Pd,(dba),CHCI, (5 mol) can be used instead of Pd(acac),.$ In our hands, using pd(PPh,), (5 mol) in THF at reflux did not furnish the product. However, with Pd(PPh,), in MeCN at reflux for 40 min, the product 2c was obtained in 79 yield. §Treatment of lc with Pd,(dba),-CHCl, (5 molx), Bu",P (5 molx), HC02NH4(1 equiv.) in THF at reflux for 30 min gave 4 and 3c in a ratio of 1 :2.4. Under the same conditions, with 2 equiv. of in HCO,NH,, the reaction of lc gave the homoallylic alcohol 2e in 73 yield. 238 J. CHEM. SOC. PERKIN TRANS. I 1994 Table 1 Pdo-Catalysed hydrogenolysis of prop-2-ynylic cyclic carbonates Conditions' Entry Substrate HCO,NH, (mol) Solvent Temp. ("C) Time (h) Product Yield ("A) la Benzene 80 3 2a 76 la THF 65 0.5 3a 93 la Benzene 25 2 3a 97 lb Benzene 80 3 2b' 74 lb Benzene 80 0.2 3b 86 lc THF 65 0.5 2c 82 lc THF 65 0.5 4+3c 93 lc Benzene 25 2 (1 :1) 4+3c 97 (5.92: 1) ~~~ All the reactions were run in the presence of Pd(acac), (5 mol) and Bu",P (5 molx).a;' Values in CHCl,: 2a, -4.4 (c4.6); 3a, -10.7 (c 1 S); 2b, -2.4 (c 2.3); 3b, -8.0 (c 3.0); 2c, -6.6 (c 2.1). The selectivity was checked by GLC analysis of the acetate of 2b using a Hewlett-Packard 5880 GCsystem column: ultra-2 (5 pheugl), 0.2 x 12m oven temp. 180-280 OC, carrier gas. He 0.6 cm3 min-'. The retention time of the acetate of 2b was 7.15 min. Yields are isolated yields. ?MOM?* 2b 5 iii.ivI 7 6 Scheme 3 Reagents and conditions: i, MOMCl, Pr',NEt, 0°C-room temp., 2 h (85); ii, 2,3-dichloro-5,6-dicyano-1 ,Cbenzoquinone (DDQ), CH,Cl,, H,O (18 : l), 30 min (96); iii, (COCI),, dimethyl sulfoxide (DMSO), Et,N, CH,Cl,, -78 "C; iv, Ph,PCHCO,Me, MeOH, 0 OC, 5 h (30 overall); v, trifluoroacetic acid FFA), CH,CI,-H,O (10: 1) (80) to afford (4R,22,62)-nona-2,6-dien-4-olide,7, Calk5 -160 (c 0.2, CHCl,) {lit.,6 a;' -162 (c 0.650, CHC13)).* Experimental Typical Procedures-Preparation of 2a. Pd(acac), and Bu",P (5 mol) were mixed in a 1 :1 ratio in dry benzene (5 cm3) to form a pale yellow solution. Then prop-2-ynylic cyclic carbonate la (303 mg, 1-00 mmol) in dry benzene (5 cm3) was added followed by ammonium formate (2.52 mg, 4.0 mmol) and the mixture was stirred for 3 h at reflux.The benzene was evaporated and then the residue was separated by SiO, column chromatography (EtOAc-hexanes, 1:3, R, 0.60) to afford alcohol 2a (199 mg, 76), Cali5 t -4.4 (c 4.6, CHCI,); 6,(3OO MHz; CDCI,$) 0.90 (3 H, t, J 7.0), 1.30 (6 H, m), 2.05 (2 H, (2H,s),5.37(1H,dt,Jlland7.3),5.48(1H,dt,Jlland7.3), 7.32 (5 H, s); v,,,(neat)/cm-' 3400 and 1620; m/z 262 (M') and 91 (base peak) (Found: C, 77.5; H, 10.0. C17H2602 requires C, 77.86; H, 9.92). Preparation of 3a. Pd(acac), and Bu",P (5 mol) were mixed in a 1 :1 ratio in dry benzene (5 cm3) to form a pale yellow solution. Then prop-2-ynylic cyclic carbonate la (303 mg, 1.OO -01) in dry benzene (5 cm3) was added followed by ammonium forrnate (63 mg, 1.0 mmol) and the mixture was stirred for 2 h at room temperature.The THF was evaporated and the residue was separated by SiO, column chromatography (EtOAc-hexanes, 1 :4, Rf 0.56) to afford alcohol 3a (252 mg, 9773, Calk5 -10.7 (c 1.5, CHCI,); 6,(300 MHz; CDCl,) 0.90 (3 H, t, J 7.1), 1.32 (4 H, m), 1.47 (2 H, m), 2.15 (2 H, m), 2.43 (2 H, m), 3.50 (1 H, dd, J9.6 and 6.7), 3.61 (1 H, dd, J9.6 and 4.0), 3.93 (1 H, m), 4.58 (2 H, s) and 7.34 (5 H, s); m/z 260 (M'), 189 (19), 91 (base peak) and 79 (11) (Found: C, 78.15; H, 9.3. C, ,H,,O requires C, 78.46; H, 9.23). Acknowledgements Generous financial support by the Korea Science and Engineering Foundation (K0SEF)-the Organic Chemistry Research Center (OCRC) is gratefully acknowledged.References 1 (a)C. Hull, S. V. Mortlook and E. J. Thomas, Tetrahedron Lett., 1987, 28,5343; (b)H. Miyake and K. Yamamura, Chem. Lett., 1993,1173. 2 J. Tsuji, T. Sugiura, M. Yuhara and I. Minami, J. Chem. Soc., Chem. Commun., 1986,922. 3 T. Mandai, T. Matsumoto, M. Kawada and J. Tsuji, Tetrahedron Lett., 1993,34,2160. 4 Recently hydrogenation of alkynes using HC0,H-NEt, in the presence of Pd,(dba),-Bu",P m),2.26(2H,m),3.34(1H,m),3.50(1H,m),3.85(1H,m),4.55 * 7: dH(300 MHz, CDCl,) 0.96 (3 H, t, J7), 2.04 (2 H, m),2.50 (2 H, m), 5.09 (1 H,m), 5.36 (1 H,m), 5.60(1 H, m), 6.14(1 H, dd, J6 and2.l)and 7.45 (1 H, dd, J6 and 1.6); v,,,(neat)/cm-' 2950,2926,2850, 1755, 1450, 1250,1240,1160,1100,830,740 and 700. f-alD Values are given in units of lo-' deg cm2 g-'. $ J Values are given in Hz. (ca.)to cis-alkenes was reported. See, K. Tani, N. One, S. Okamoto and F. Sato, J. Chem. SOC.,Chem. Commun.,1993,386. 5 S.-K. Kang, S.-G. Kim and D.-G. Cho, Tetrahedron: Asymmetry, 1992,3, 1509. 6 Y.Miyashita and K. Mori, Agric. Biol. Chem., 1981,45,2521. Paper 3/0639 1 G Received 26th October 1993 Accepted 30th November 1993
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