Synthesis and Diels-Alder reactions of homochiral 2-sulfinylmaleates with cyclopentadiene |
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Authors: | Ins Alonso M Beln Cid J Carlos Carretero Jos L Garcia Ruano Miguel A Hoyos |
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Institution: | Departamento de Química (C-I), Universidad Autónoma, Cantoblanco, 28049- Madrid, Spain |
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Abstract: | Enantiomerically pure 2-p-tolylsulfinylmaleates 1, 2 and 3 have been readily prepared by Knoevenagel reaction between (S)-menthyl p-toluenesulfinate and glyoxylic acid. Their asymmetric Diels-Alder reactions with cyclopentadiene have been studied under a wide range of uncatalyzed and catalyzed conditions and the stereochemical results have been explained by assuming a steric control approach, in term of S-cis or S-trans favoured conformations. Uncatalyzed Diels-Alder reactions of 1 and some Lewis acid catalyzed Diels-Alder reactions of 2 show high facial and endo selectivities. The facial selectivity of dienophile 2 highly depends on the Lewis acid, whereas reactivity of 1 and 3 is very sensitive to the solvent. These sulfinylmaleates 1, 2 and 3 act as synthetic equivalents of chiral acetylenedicarboxylates in Diels-Alder reactions after basic elimination of the sulfinylic moiety in the resulting adducts. |
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