Synthesis of dl-α-Tocopherol by Cross Coupling Reaction of Ene-type Chloride with the C10-Grignard Reagent

Ene-type chloride (5 a) was prepared with trichloroisocyanuric acid as a chlorination reagent from pentenylchromanol (3), obtained from myrcene and 2, 3, 5-trimethylhydroquinone in 3 steps. Chloride (5 a) reacted with 3, 7-dimethyloctylmagnesium bromide in the presence of CuCl (I) as the catalyst in THE to afford mixture consisting of SN2' type cross coupling products (7 a) and (8 a) with high regioselectivity. Compounds (5 b-e) reacted with the Grignard reagent in the presence of CuCl (I) to give SN2' type cross coupling products (7) and (8) with high regioselectivity Table-1. dl-α-Tocopherol was prepared in good yields by the hydrogenation of compounds (7 a) and (8 a).