Hmc. Ferraz et Lf. Silva, Construction of functionalized indans by thallium(III) promoted ring contraction of 3-alkenols, TETRAHEDRON, 57(50), 2001, pp. 9939-9949
An efficient four step protocol for the construction of functionalized inda
ns was developed. 1-Tetralones were transformed into unsaturated esters by
Reformatsky reaction with bromo-esters (ethyl 2-bromopropionate, ethyl brom
oacetate or ethyl 2-bromobutyrate), followed by dehydration of the beta -hy
droxy-ester formed. Reduction of the ester moiety led to homoallylic alcoho
ls bearing an endocyclic double bond. The oxidative rearrangement of these
3-alkenols was performed by thallium trinitrate (TTN) in a 2:1 mixture of A
cOH/H2O, leading to the ring contraction products in moderate to very good
yield. Fourteen examples of this sequence were studied. The oxidation of 3-
alkenols prepared from 2-tetralones with TTN was also investigated. With th
ese substrates the ring contraction reaction was not observed. (C) 2001 Els
evier Science Ltd. All rights reserved.