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A convenient, stereospecific synthesis of racemic juvenile hormones and some of their analogues via vinylcuprates

1981; Royal Netherlands Chemical Society; Volume: 100; Issue: 7-8 Linguagem: Inglês

10.1002/recl.19811000702

1878-7096

H. KLEIJN, H. Westmijze, J. Meijer, P. Vermeer,

Asymmetric Synthesis and Catalysis

Abstract This paper describes a stereospecific synthesis of nine 2 E ,6 E , 10( Z )‐trienyl esters R 1 R 2 CCH(CH 2 ) 2 CR 3 CH(CH 2 ) 2 CR 4 CHCO 2 Me ( 1a‐i ) and their selective conversion into the corresponding epoxides magnified image ( 7a‐i ), including the natural occurring hormones JHI‐III. The trienyl system of 1 has been reached stereospecifically by allowing specifically substituted vinylcuprates, [R 1 R 2 CCHCuY] ⊖ , to react with 4‐iodo‐1‐butyne, followed by conversion of the formed enynes R 1 R 2 CCH(CH 2 ) 2 CCH (3) into new cuprates of the type thus [R 1 R 2 CCH(CH 2 ) 2 CR 3 CHCuY] ⊖ . These cuprates furnish, upon reaction with 4‐iodo‐l‐butyne, the dienynes R 1 R 2 CCH(CH 2 ) 2 CR 3 CH(CH 2 ) 2 CCH ( 5 ). From 5 , vinylcuprates [R 1 R 2 CCH(CH 2 ) 2 CR 3 CH(CH 2 ) 2 CR 4 CHCuY] ⊖ have been obtained which, upon reaction with carbon dioxide followed by methylation, gave compounds 1 . For the preparation of the vinylcuprates from the 1‐alkynes we generally used a new alkylcopper( I ) species of the type R 3 Cu 2 MgX. The epoxidation of 1 into 7 was performed using a literature procedure.