82787-99-3Relevant articles and documents
REACTION OF BENZOTHIOPHENE-5- AND 6-METHANOLS WITH n-BUTYLLITHIUM. DIRECTED LITHIATION IN THE BENZENE RING
Cross, Peter E.,Dickinson, Roger P.
, p. 2391 - 2400 (2007/10/02)
The preparation of 3-methylbenzothiophene-6-methanol (3) is described.Treatment of 3 with n-butyllithium followed by CO2 gave, in addition to the expected 2-carboxylic acid 2, a substantial quantity of the lactone 11 formed via lithiation at the 7-position.It was concluded that lithiation at 7-position is favoured by a co-operative effect of the anion of the alcohol and the ring sulphur atom, as well as the 3-methyl group which reduces the rate of lithiation at the 2-position.In the case of compounds in which the alcohol group is at the 5-position or which lack the 3-methyl group, lithiation in the benzene ring was much less favoured .