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A stereoselective synthesis of 3-phenoxybenzyl (±)-cis and trans-3-(2,2-dichlorovinyl)-2,2-dimethyl-1-cyclopropanecarboxylic acid starting from readily available 2-methyl-3-buten-2-ol(2) is described. Allylic rearrangement of 2-methyl-3-buten-2-ol, in the presence of acetic acid and acetic anhydride gave 3-methyl-2-butenyl acetate(3). The [3,3] sigmatropic rearrangement of the allyl acetate(3), as the silylketene acetal, produced the γ,δ-unsaturated acid(4). Treatment of 3,3-dimethyl-4-pentenoic acid(4) with SOCl2 followed by esterification with 3-phenoxybenzyl alcohol yielded 3, 3-dimethyl-4-pentenoic acid ester(5). Addition of carbon tetrachloride to the olefin ester(6) furnished 4,6,6,6-tetrachloro-3,3-dimethylhexanoic acid ester (7). Cyclization with potassium t-butoxide and elimination of hydrogen chloride afforded 3-phenoxybenzyl (±) cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethyl-1-cyclopropanecarboxylic acid.
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