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

The hetero-Diels-Alder addition Of SO2 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 SO2 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 DELTADELTAG = 3.9 kcal/mol was evaluated at -60-degrees 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.


Published in:
Helvetica Chimica Acta, 76, 6, 2250-2253
Year:
1993
ISSN:
0018-019X
Keywords:
Note:
Univ lausanne,chim sect,2 rue barre,ch-1005 lausanne,switzerland.
Laboratories:




 Record created 2005-11-09, last modified 2018-03-17


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