Δ 3-Dihydropyrans and tetrahydropyrans by reduction of pyrylium salts with sodium borohydride in acetic acid

TS Balaban, AT Balaban

Index: Balaban, Teodor-Silviu; Balaban, Alexandru, T. Tetrahedron Letters, 1987 , vol. 28, # 12 p. 1341 - 1344

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Citation Number: 19

Abstract

The major reduction products with triacetoxyborohydride (NaBH 4 in AcOH) of 2,4,6-trisubstituted pyrylium salts bearing alkyl substituents in the 2- and/or 6- position are the Δ 3 -dihydropyrans with 2- and 6- substituents and the all- -2,4,6-trisubstituted tetrahydropyrans. Δ 3 -Dihydropyrans are shown to be formed 2H-pyrans by a 1,4 reduction while tetrahydropyrans result from 4H-pyrans by reduction of both enol-ether double bonds. ... – ) or by TLC ( – ), and were ...