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Reductive Radical Cyclisations of Bromo Acetals and (Bromomethyl)silyl Ethers of Terpenoid Alcohols
Author(s) -
Lee Edward R.,
Lakomy Ivo,
Bigler Peter,
Scheffold Rolf
Publication year - 1991
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19910740117
Subject(s) - chemistry , allylic rearrangement , radical , silylation , acetaldehyde , hydride , tin , terpenoid , medicinal chemistry , reductive elimination , stereochemistry , organic chemistry , catalysis , ethanol , hydrogen
The tin hydride promoted and the reductive vitamin B 12 catalysed radical cyclisation of mixed 2‐bromo‐acetaldehyde acetals and of (2‐bromomethyl)dimethylsilyl ethers of allylic terpenoid alcohols has been investigated: 3‐oxadeca‐5,9‐dien‐l‐yl radicals undergo 5‐‘ exo ’ cyclisation to oxolanes ( Scheme 4 ), 3‐oxa‐2‐siladeca‐5,9‐dien‐1‐yl radicals sequential 6‐‘ endo ’→5‐‘ exo ’ tandem cyclisation to cis ‐3‐oxa‐4‐silabicyclo[4.3.0]nonanes ( Scheme 5 ), and 3‐oxa‐2‐silatetradeca‐5,9,13‐trien‐l‐yl radicals sequential 6‐‘ endo ’→6‐‘ endo ’→5‐‘ exo ’ triple cyclisation to trans ‐ transoid ‐ trans ‐ 12‐oxa‐11‐silatricyclo[7.4.0.0 2,6 ] tridecanes ( Scheme 6 ).