Open AccessMechanistic Studies on the Base-Promoted Conversion of Alkoxy-Substituted, Ring-Fused gem-Dihalocyclopropanes into Furans: Evidence for a Process Involving Electrocyclic Ring Closure of a Carbonyl Ylide Intermediate
Author(s) -
Phillip P. Sharp,
Jiří Mikušek,
Junming Ho,
Elizabeth H. Krenske,
Martin G. Banwell,
Michelle L. Coote,
Jas S. Ward,
Anthony C. Willis
Publication year - 2018
Publication title -
the journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.2
H-Index - 228
eISSN - 1520-6904
pISSN - 0022-3263
DOI - 10.1021/acs.joc.8b01766
Subject(s) - chemistry , dehydrohalogenation , ylide , ring (chemistry) , alkoxy group , carbanion , base (topology) , medicinal chemistry , amidine , deprotonation , stereochemistry , photochemistry , organic chemistry , catalysis , ion , mathematical analysis , alkyl , mathematics
The mechanism associated with the base-promoted conversion of alkoxy-substituted and ring-fused gem-dihalocyclopropanes such as 40 into annulated furans has been explored. Treatment of compound 40 with potassium tert-butoxide affords a mixture of furans 23/27 and 41, an outcome that suggests the intermediacy of the slowly interconverting carbonyl ylides 42 and 43 that undergo rapid [1,5]-electrocyclizations and subsequent dehydrohalogenation to afford the observed products. This proposal is supported by ab initio MO and DFT calculations that also suggest a vinylcarbene insertion pathway is less likely to be operative.
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