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Stabilizing Effect by Geminal Dioxy Substitution and Anomeric Effect in 3,6-Dihydro-6-methoxy-1,2-oxathiin 2-Oxides

✍ Scribed by Brigitte Deguin; Pierre Vogel

Book ID
102254303
Publisher
John Wiley and Sons
Year
1993
Tongue
German
Weight
243 KB
Volume
76
Category
Article
ISSN
0018-019X

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✦ Synopsis

Abstract

The hetero‐Diels‐Alder addition of SO~2~ to (E)‐hexa‐1,3‐diene (4) gives first 6‐ethyl‐3,6‐dihydro‐1,2‐oxathiin 2‐oxide (= 6‐ethylsultine) with the Et group occupying a pseudoaxial position, and then the more stable stereoisomer 6 with the Et substituent in a pseudoequatorial position. The SO~2~ additions to 1‐methoxybuta‐1,3‐diene (7) and to 1‐methoxy‐3‐[(trimethylsilyl)oxy]buta‐1,3‐diene (8) give the 6‐methoxysultines 9 and 10, respectively, with the MeO groups in pseudoaxial positions and which do not equilibrate with sultines having pseudoequatorial MeO substituents (anomeric effect). A lower limit of ΔΔ__G__ = 3.9 kcal/mol was evaluated at −60° for the stabilizing effect arising from the geminal vicinity of a MeO and sulfinate moiety in 3,6‐dihydro‐6‐methoxy‐4‐[(trimethylsilyl)oxy]‐1,2‐oxathiin 2‐oxide.

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## Abstract The rates of photo‐oxidation of exocyclic __S‐cis__‐butadienes grafted onto bicyclo‐[2.2.1]heptanes and 7‐oxabicyclo[2.2.1]heptanes (**1–6**) are dependent upon remote modifications of the bicyclic skeletons. They correlate with the rates of __Diels‐Alder__ additions of these dienes to