SCHEDULED MAINTENANCE
Electrophilic substitution in indoles. Part 13. The synthesis and rearrangement of 2-deuteriospiro[cyclopentane-3′-indolenine]
Abstract
2-Deuterioindole was prepared from N-phenylsulphonylindole by lithiation, quenching with D2O, and hydrolysis. Treatment of the 2-deuterioindole Grignard reagent with succinic anhydride gave 4-(indol-3-yl)-4-oxobutanoic acid with partial loss of the deuterium from the 2-position. 2,3-Dideuterioindole (prepared by acid-catalysed deuteriation of 2-deuterioindole) when treated in the same way, gave the indolyl oxobutanoic acid, 92% deuteriated at the indolyl 2-position. Reduction to the deuterioindolylbutanol and treatment of its toluene-p-sulphonate with potassium t-butoxide give 2-deuterio-spiro[cyclopentane-3′-(3H) indole] which was 88% deuteriated at the 2-position. The kinetics of the acid-catalysed rearrangement of the deuterioindolenine and its non-deuteriated analogue were measured and the ratio kH/kD of the pseudo-first-order rate constants was found to be 1.08, showing that the isotope effect was very small.
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