Unusual reactions of 2-methyltellurocyclohexene-1-carbaldehyde with phenacyl bromides

Abstract

Reactions of dialkyl and alkyl aryl tellurides R 1 R 2 Te (R 1 and R 2 = Alk; R 1 = Alk, R 2 = Ar) with phenacyl bromides in the molar ratio 1 : 1 usually yield telluro nium salts R 1 R 2 (ArCOCH 2 )Te + Br -1 (X ray diffrac tion data 2 ). Divinyl telluride (CH 2 =CH) 2 Te reacts with alkyl iodides to give divinylalkyltelluronium salts (CH 2 =CH) 2 AlkTe + I -. 3 Reactions of 2 methyltelluro cyclohexene 1 carbaldehyde (1) 4,5 with phenacyl bro mides 2 occur in an absolutely different fashion. Heating of an equimolar mixture of these reagents in boiling etha nol gave earlier unknown 3 aroylmethyl 1 bromo 1 methyl 1,3,4,5,6,7 hexahydro 2,1λ 4 benzoxatelluroles (3) in 45-60% yields. The reaction rate is determined by the nature of the p substituent in the arene ring of phenacyl bromide, decreasing in the order NO 2 > H > OMe. The 1 H, 13 C, and 125 Te NMR spectra of heterocycles 3 suggest that they are composed of two diastereomers. Ar = Ph (a), 4 NO 2 C 6 H 4 (b), 4 MeOC 6 H 4 (c)