Green synthesis of novel isatin thioketal derivatives under solvent-free conditions

Figures & data

Scheme 1. Alkylation of isatin thioketal by Michael reaction and direct method.

Table 1. Aza-Michael addition of spiro[[1,3]dithiolane-2,3′-indolin]-2′-one 1 to α,β-unsaturated esters 2 under solvent-free conditions.

Entry	Ester 2	Product 3	Time (min)	Yield (%)^a
1			120	90
2			120	85
3			120	90
4			120	80
5			120	75
6			120	65
7			150	70
8			150	65
9			150	63
10			150	50

^aIsolated yields.

Table 2. N-alkylation of spiro[[1,3]dithiolane-2,3′-indolin]-2′-one 1 by dihaloalkanes 4 under solvent-free conditions.

Entry	dihaloalkane 4	Product 5	Time (min)	Yield (%)^a
1			120	80
2			120	85
3			120	80
4			120	85
5			120	75

^aIsolated yields.

Scheme 2. Aza-Michael addition of spiro[[1,3]dithiolane-2,3′-indolin]-2′-one 1 to n-butyl acrylate 2c as model reaction.

Scheme 3. Direct N-alkylation reaction of spiro[[1,3]dithiolane-2,3′-indolin]-2′-one 1 with 1,6-dibromohexane 4d (as a model reaction).

Scheme 4. Proposed mechanism for the formation of 3 and 5.