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Sn/Li Exchange Reactions in 1,ω‐Distannylated Conjugated Trienes and Tetraenes: An Enabling Step for Polyene Synthesis
Author(s) -
Burghart Jochen,
Brückner Reinhard
Publication year - 2011
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201001231
Subject(s) - chemistry , polyene , negishi coupling , conjugated system , metalation , stereochemistry , medicinal chemistry , enyne , dimer , nuclear magnetic resonance spectroscopy , organic chemistry , catalysis , polymer
Successive treatments of (1 E ,3 E ,5 E )‐ or (1 E ,3 Z ,5 E )‐1,6‐bis(tributylstannyl)hexa‐1,3,5‐triene with n BuLi and butanal rendered polyenyl alcohols resulting from one Sn/Li exchange reaction and exhibiting complete retention of the configuration of all C=C bonds. Mono‐ or dimethylated all‐ E ‐configured 1,6‐distannylated conjugated trienes as well as all‐ E ‐1,8‐bis(tributylstannyl)octa‐1,3,5,7‐tetraene and dimethylated congeners thereof reacted similarly. The respective Sn/Li exchange reactions affected the substructure Bu 3 Sn–CH=CH with a 93–94:7–6 preference over Bu 3 Sn–CMe=CH and with a 90:10 preference over Bu 3 Sn–CH=CMe. all‐ E ‐1‐Lithio‐6‐(tributylstannyl)hexa‐1,3,5‐triene was incorporated into navenone B after Negishi coupling and into (–)‐cicutoxin after acylation. NMR spectroscopy of our navenone B specimen revealed that certain resonances were misassigned previously.