Convenient preparation of A-ring fused pyridines from steroidal enamides

Synthesis of D-Ring Annulated Pyridosteroids from β-Formyl Enamides and Their Biological Evaluations

“…20 Enamides are also utilized for the preparation of pyridosteroids by the reaction of Vilsmeier reagent. 21 Most of the reactions involve the electron deficient carbonyl of N-acetyl group via intermolecular cycloaddition reactions. 22 On the other hand, β-formyl enamides have emerged as interesting synthons for their potential diversity in heterocyclic synthesis.…”

“…35 Recently, polysubstituted steroidal pyridines were evaluated for cytotoxic potential of prostate cancer cell lines using androgen inhibitor abiraterone as control drug (Figure 1). 36 In continuation of our interests in steroidal β-formyl enamides, 21,23,24 herein, we report the synthesis of a new series of D-ring-fused pyridosteroids, and evaluation of their cytotoxic activities by inducing apoptosis against prostate cancer cells. The novel androst [17,16-b]pyridine and nonsteroidal pyridine derivatives were derived from the reaction of corresponding βformyl enamides 37−39 with alkynes.…”

“…Enamides constitute the building block of many biologically active compounds and attract considerable attention as prochiral substrates in asymmetric synthesis of amino acids. , Few metal-catalyzed coupling reactions of enamides with alkynes have been reported for synthesis of pyridine through amide activation reaction . Enamides are also utilized for the preparation of pyridosteroids by the reaction of Vilsmeier reagent . Most of the reactions involve the electron deficient carbonyl of N-acetyl group via intermolecular cycloaddition reactions …”

“…In continuation of our interests in steroidal β-formyl enamides, ,, herein, we report the synthesis of a new series of D-ring-fused pyridosteroids, and evaluation of their cytotoxic activities by inducing apoptosis against prostate cancer cells. The novel androst­[17,16- b ]­pyridine and nonsteroidal pyridine derivatives were derived from the reaction of corresponding β-formyl enamides − with alkynes.…”

A Rapid and Convenient Microwave-Promoted Synthesis of 3,5-Disubstituted 2-Chloropyridines and Their Conversion into Tetrazolo[1,5-a]pyridines

“…Moreover, this method is significantly advantageous over a previously reported Vilsmeier reaction, where maintaining the reaction temperature at -5 °C to 0 °C was not necessary for the in situ generation of the chloromethyleneiminium salt (the Vilsmeier reagent), which is a prerequisite in all classical Vilsmeier reactions. 19 In addition, these newly synthesized compounds were converted into the corresponding tetrazolo[1,5a]pyridines by microwave-mediated solid-phase reaction in presence of an acid catalyst in moderate to good yields.…”