Cobalt-Mediated Cyclooligomerization Reactions of Borylacetylenes

摘要

Reaction of bis(diethylamino)acetylene (1) with lithium and chlorobis(dimethylamino)borane yields 1-[bis(dimethylami-no)boryl]-2-(diethylamino)acetylene (2).Treatment of 1-aryl-2-(trimethylstannyl)acetylenes 3 with chlorobisfdiisopropyl-amino)borane results in the quantitative formation of 1-aryl-2-[bis(diisopropylamino)boryl]acetylene compounds 4.The 1-aryl-2-borylacetylene derivatives 5,6,and 7 are obtained by the reaction of 3 with the appropriate haloborane,or by reacting 4 with two equivalents of HC1 and one equivalent of catechol,dithiocatechol and 2-hydroxythiophenol.The catalytic cyclotrimerizations of 5a-d with [CpCo(CO)_2] or [Co_2(CO)_8] lead to isomeric mixtures of the triborylbenzene derivatives 8a-d and 8a'-d',whereas 6a-d and 7a-b undergo cyclotrimerization only with catalytic amount of [Co_2(CO)_8],to give isomeric mixtures of the triborylbenzene derivatives 12a-d/12a'-d' and 13a-b/13a'-b',respectively.The reaction of 2 with a stoichiometric amount of (eta~5-cyclo-pentadienyl)bis(ethene)cobalt leads to (eta~5-cyclopenta-dienyl)(eta~4-cyclobutadiene)cobalt complexes 9.The analogous complexes 10 and 11 are obtained by the reactions of 6 and 7 with a stoichiometric amount of (eta~5-cyclopentadienyl)di-carbonylcobalt.Treatment of Co_2(CO)_8 with 5a,6a,and 7a yields the dicobaltatetrahedranes 14a,15a and 16a.Compound 15a reacts with two equivalents of diphenylacetylene and l-(l,3,2-benzodioxaborolyl)-2-phenylacetylene (5a),to furnish (l,3,2-benzodithiaborolyl)pentaphenylbenzene (17) and bis(l,3,2-benzodioxaborolyl)(l,3,2-benzodithiaborolyl)-triphenylbenzene (18),respectively.The new compounds have been characterized by NMR spectroscopy and mass spectrometry,as well as by X-ray structural analyses for 4a,5a,6a,and 10a.