Some Diels-Alder adducts of 6-vinyl-1-oxa-4-thiaspiro[4.5]dec-6-ene

Abstract

6-Vinyl-1-oxa-4-thiaspiro[4.5]dec-6-ene has been reacted with dienophiles, such as N-phenylmaleimide (NPM), N-methyltriazoline-2,5-dione (MTAD) and dimethylacetylene dicarboxylate (DMAD), to assess the 1,3-diastereofacial selection caused by the acetal function. In each case, a mixture of two diastereoisomers was produced. The crystal structures of the products of the addition of NPM and MTAD syn to the acetal oxygen, 2-phenyl-2,3,3a,4,5,5a,6,7,8,9,9a,9b-dodecahydro-1H-benz[e] isoindole-6-spiro-2'-[1',3']oxathiolane-1,3-dione, C₂₀H₂₁NO₃S, (IIa), and 2-methyl-5,7,8,9,10,10a-hexahydro-1H-1,2,4-triazolo[1,2-a] cinnoline-7-spiro-2'-[1',3']oxathiolane-1,3- dione, C₁₃H₁₇N₃O₃S, (IIIa), respectively, and the product of the addition of DMAD syn to the acetal sulfur, dimethyl 1,2,3,4,4a,7-hexahydronaphthalene-1-spiro-2'-[1',3']oxathiolane-5,6-dicarboxylate, C₁₆H₂₀O₅S, (IVb), have been determined. All three structures are composed of independent molecules separated by normal van der Waals distances. The 1-oxa-4-thia heterocyclic ring has an envelope conformation in the three structures and the S-Csp³ bond distances differ significantly from each other, as observed in comparable structures; the remaining molecular dimensions are as expected.