Condensation of 4-chloro-2H-chromene-3-carbaldehydes and ethyl-3-aminocrotonates with p-TsOH: a facile approach for the synthesis of chromenyldihydropyridines

Abstract

The investigated reaction of 4-chloro-2H-chromene-3-carbaldehyde 1a with ethyl 3-oxobutanoate 2a in the presence of ammonium acetate provided two compounds, 2H-chromenyldihydropyridine dicarboxylate 3a and chromenopyridine carboxylate 4a. However, the reaction of 1a with ethyl-3-aminocrotonate 5a in the presence of p-TsOH provided selectively 2H-chromenyldihydropyridine dicarboxylate 3a with very good yield. The established method was applied for the preparation of series of 2H-chromenyldihydropyridine dicarboxylates 3a–q.

GRAPHICAL ABSTRACT

KEYWORDS:

• 4-Chloro-2H-chromene-3-carbaldehydes
• ethyl-3-aminocrotonates
• 2H-chromenyldihydropyridine dicarboxylates
• p-TsOH

Acknowledgment

The authors thank Director, CSIR-IICT for constant encouragement and support.

Additional information

Funding

B. China Raju acknowledges SERB, New Delhi for financial support [EEQ/2017/000314]. IICT manuscript communication no. IICT/Pubs./2018/265.