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Synthesis of Vinylallenes by Conjugate 1,6‐, 1,8‐, 1,10‐ and 1,12‐Addition Reactions of Organocuprates with Acetylenic Michael Acceptors and Their Use as Dienes in Intermolecular Diels‐Alder Reactions
Author(s) -
Koop Ulrich,
Handke Gabriele,
Krause Norbert
Publication year - 1996
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199619961002
Subject(s) - chemistry , conjugate , intermolecular force , addition reaction , diels–alder reaction , organic chemistry , catalysis , molecule , mathematical analysis , mathematics
Various vinylallenes were synthesized by conjugate cuprate additions to acetylenic Michael acceptors. Thus, 1,6‐addition reactions with 2‐en‐4‐ynoates 1, 3 , and 5a , respectively, furnished vinylallenes 2, 4 , and 7 after regioselective electrophilic capture of the allenyl enolates formed. Likewise, 1,8‐addition to 2,4‐dien‐6‐ynoates 8a and 10 gave the vinylallenes 9 and 11 , whereas the 1,10‐addition of Me 2 CuLi to 2,4,6‐trien‐8‐ynoate 12 provided allene 13 , and the analogous 1,12‐addition to 2,4,6,8‐tetraen‐10‐ynoate 14 furnished the polyene 15 . These vinylallenes are valuable dienophiles in regio‐ and stereoselective Diels‐Alder reactions, as evidenced by the formation of the cycloaddition products 16–24 . In the presence of Lewis acids, vinylallene 4a presumably rearranges to a cyclopentadiene derivative which then forms the cycloadducts 25 and 26 .