Chemistry of polyhalogenated nitrobutadienes, 14: Efficient synthesis of functionalized (Z)-2-allylidenethiazolidin-4-ones

Abstract

The reaction of mercaptoacetic acid esters with pentachloro-2-nitro-1,3-butadiene (1) provides an appropriate precursor for the synthesis of special thiazolidin-4-ones. Applying different anilines as the second constituent for the requisite cyclization step, a series of (Z)-2-allylidenethiazolidin-4-ones was obtained in yields up to 81%. Some subsequent reactions have been examined too, such as the formation of perfunctionalized 1H-pyrazoles upon treatment with hydrazine. Thiazolidinones are as well known for their physiological activities as for their application in optoelectronics.

Keywords: 1H-pyrazoles; 2-nitroperchlorobutadiene; atropisomers; cyclization; thiazolidin-4-ones.

Scheme 1

S_NVin reactions of pentachloro-2-nitro-1,3-butadiene (1).

Scheme 2

Formation of thiazolidin-4-ones 7–19.

Figure 1

Hindered rotation in the case of ortho- or meta-substituted aniline precursors.

Figure 2

X-ray analysis of thiazolidin-4-one 11.

Scheme 3

Assumed mechanism for the formation of thiazolidin-4-ones 7–18.

Scheme 4

Substitution reactions of the precursors 3 and 5 with additional amines.

Scheme 5

Synthesis of 5-arylmethylidenethiazolidin-4-ones 22–26 and 1H-pyrazoles 27, 28.

Scheme 6

Assumed mechanism for the formation of 1H-pyrazole 27.

Scheme 7

Formation of ethyl propanoate 29 and subsequent reactions.