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Regioselective Electrophilic Additions of Bicyclo[2.2. n ]alk‐2‐enes Controlled by Remote Epoxide Functions
Author(s) -
Claret François,
Carrupt PierreAlain,
Vogel Pierre
Publication year - 1987
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.19870700723
Subject(s) - chemistry , bicyclic molecule , regioselectivity , epoxide , electrophile , octane , alkene , stereochemistry , medicinal chemistry , ring (chemistry) , organic chemistry , catalysis
The electrophilic additions of 2‐nitrobenzenesulfenyl chloride to (1 RS ,2 SR ,4 RS )‐spiro[bicyclo[2.2.1]hept‐5‐ene‐2,2′‐oxirane] ( 12 ) and (1 RS ,2 SR ,4 RS )‐spiro[bicyclo[2.2.2]oct‐5‐ene‐2,2′‐oxirane] ( 14 ) were not regioselective under condition of kinetic control. However, good regioselectivity was observed for the addition of 2‐nitro‐benzenesulfenyl chloride to (1 RS ,2 RS ,4 RS )‐spiro[bicyclo[2.2.1]hept‐5‐ene‐2,2′‐oxirane] ( 13 ), giving (1 RS ,2 SR ,4 SR ,5 RS ,6 RS )‐6‐ exo ‐(2‐nitrophenylthio)spiro[bicyclo[2.2.1]heptane‐2.2′‐oxirane]‐5‐endo‐yl chloride ( 24 ) and for the exo addition to (1 RS ,2 RS .4 RS )‐spiro[bicyclo[2.2.2]oct05‐ene‐2,2′‐oxirane] ( 15 ), giving preferntially (1 RS ,2 SR ,4 SR ,5 RS ,6 RS )‐6‐ exo ‐(2‐nitrophenylthio) spiro[bicyxlo[2.2.2]octane‐2,2′‐oxirane]‐5‐endo‐yl chloride ( 30 ). The facial selectivity (electrophilic exo vs. endo attack on the bucyclic alkene) depended on the relative configuration of the spiroepoxide ring in the bicyclo[2.2.2]octenes 14 and 15 . The exo ‐epoxide 14 was attacked preferentially (6:1) on the endo face by sulfenyl whereas exo attack was preferred (7:2) in the case of the endo ‐epoxide 15 . No products resulting from transannular ring expansion of the spiro‐epoxide moieties could be detected.