Abstract

78
C. Lawrence, I. M. Bell, C. Abell and F. J. Leeper
"Approaches to Antibody-catalysed Cationic Cyclisations: Chemical Studies of Leaving Groups and Cyclisation Modes"
Isr. J. Chem.,1996, 36, 161-169.

The solvolysis of a range of esters of 2-methylbenzyl alcohol has been studied. It was found that sulphonate esters are solvolysed very rapidly in aqueous solution (t_1/2 ca. 35 s) whereas sulphinates react slowly (t_1/2 ca. 35 h) and a phosphonate diester is stable. The fluorescent 5-dimethylaminonaphthalene-1-sulphinate (dansinate) esters held the most promise as substrates for antibody-catalysed cationic cyclisations. It was shown by 18O-labelling studies that ester is hydrolysed predominantly (but not exclusively) by S_N1 reaction at the benzylic position. A number of conditions were tried to effect cationic cyclisations of an unsaturated benzylic alcohol, whose ester is intended as the substrate for the antibody-catalysed reaction. The products obtained were the result of attack of the non-benzylic alcohol on either the benzylic cation, to give 31 and 32, or on the protonated alkene, to give 29. No cyclisation of the alkene onto the benzylic cation, to give 4, was observed, suggesting that this is a disfavoured reaction in solution.

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