Bovine serum albumin: An efficient and green biocatalyst for the one-pot four-component synthesis of pyrano[2,3-c]pyrazoles

Abstract

The use of biocatalysts is attracting an increasing amount of attention in chemical catalysis. Here, we have shown that bovine serum albumin (BSA), a ubiquitous, inexpensive, non-enzymatic transport protein, can serve as an efficient, retrievable catalyst in the one-pot four-component reaction of aryl aldehydes, malononitrile, hydrazine hydrate, and ethyl acetoacetate for the synthesis of pyrano[2,3-c]pyrazoles under mild reaction conditions. The BSA biocatalyst also displayed a high catalytic affinity for acyclic/cyclic ketones to yield the corresponding pyrano[2,3-c]pyrazoles or their spirocyclic variants. The BSA could be used for at least five cycles without serious loss of catalytic activity. This novel, efficient protocol has the merits of high yield, operational simplicity, and a relatively benign environmental impact. Moreover, the method extends the promiscuity of BSA as a biocatalyst.