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Part-A Studies on 2-methyl indoline derivatives…..
Spang et. al. 124 carried out formylation on 2-methyl indoline and
prepared Schiff bases using differently substituted primary aromatic amines.
Indolines such as (1), (2), and (3) were prepared efficiently by Nicolaou
et. al. 125 on solid supports by reaction of a resin-based selenyl bromide with
substituted o-allylaniline derivatives to give resin-bound selenylmethyl indoline
derivatives which could be functionalized and reductively cleaved to give
methylindoline derivatives. The supported selenylmethyl indoline
intermediates could either be cleaved directly by Bu3SnH-mediated reduction
to 2-methylindolines, acylated with phosgene and amines and reductive
cleaved with Bu3SnH to give methylindoline urea derivatives, or acylated with
alkenoic acids or alkylated with allylic bromides to give amide and amine
derivatives which underwent stereoselective radical cyclization upon resin
cleavage to give polycyclic indolines. Treatment of o-allylaniline with resinbound
selenyl bromide in the presence of SnCl4 gave a resin-bound
selenylmethyl indoline; reduction of the resin-bound indoline with tributyltin
hydride in the presence of AIBN gave (1) in 89% purity. Treatment of the
resin-bound selenylmethyl indoline with a toluene solution of phosgene
followed by addition of triethylamine and piperazine gave a resin-bound
indoline urea derivative, which was acylated with 1-naphthalenecarboxylic
acid and DCC and reductively cleaved with Bu3SnH in the presence of AIBN
to give piperazinylcarbonyl methylindoline (2) in 19% yield. Treatment of the
resin-bound selenylmethyl indoline with MeCH=CHCH2Br and sodium hydride
gave a resin-bound crotylindoline methylselenyl derivative which underwent
stereoselective radical cyclization and cleavage to give
tetrahydropyrroloindoline derivative (3) in 19% yield. The solid phase
preparation of indolines cleavable by radical reduction allowed for the facile
preparation of medicinally valuable methyl indoline derivatives and for the
assembly of complex indoline natural product derivatives. Preparation of
methyl indoline derivatives on solid phase allowed access to combinatorial
libraries of structurally complex indoline derivatives. (Fig. A.10)
Department of Chemistry, Saurashtra University, Rajkot – 360 005 22