Diastereoselective Generation of C₂-Azlactonized 2H-Chromenes via Brønsted Acid-Catalyzed Oxo-Cyclization of Propargyl Alcohols

Abstract

A new Brønsted acid-catalyzed oxo-cyclization of propargyl alcohols with azlactones to synthesize C 2 -azlactonized 2H-chromenes has been established that uses 1,1′-binaphthyl-2,2′diyl hydrogen phosphate (BiNPO 4 H) as the catalyst and gives excellent diastereoselectivities (≥19:1 dr) in most cases. This protocol has a high compatibility with various substituents of substrates, offering a catalytic and useful entry to the fabrication of the synthetically important C 2 -functionalized 2H-chromene scaffold.α-Substituted 2H-chromenes and their analogs represent a valuable class of privileged oxo-containing heterocycles that are frequently encountered in a wide assortment of natural products, such as gaudichaudianic acid 1 and (+)-myristinin A, 2 and synthetic pharmaceuticals demonstrating antipsychotic, antibacterial, antifungal, antiviral, anticancer, antioxidative, antidepressive, antihypertensive, and antidiabetic activities (Figure 1). 3,4 Moreover, 2H-chromene derivatives

Cascade Cyclization of 1,5-Diynols and (RO)2P(O)SH to Construct Benzo[b]fluorenyl S-Alkyl Phosphorothioates under Catalyst-Free Conditions

“…Propargylic alcohols are considered one of the most versatile synthons in synthetic chemistry. 11 The cascade reactions of propargylic alcohols have emerged as a powerful strategy for the rapid construction of functionalized carbo-and heterocyclic frameworks in the past few decades. 12 The direct transformation of propargylic alcohols into diverse organo- thiophosphates is highly attractive yet challenging.…”

Cu(II)-Catalyzed [3 + 1 + 1 + 1] Cyclization of 1,3-Diketones and 2-Naphthols Using N,N-Dimethylethanolamine as a Dual Carbon Synthon for the Synthesis of 2H-Chromenes

“…Hence, the development of methodologies for the synthesis of 2 H -chromene derivatives has evoked great interest in the realms of organic synthesis and chemical biology. Diverse accesses to 2 H -chromene derivatives have been realized . Generally, there are two types of methods for constructing 2 H -chromenes, one involving benzopyran ring formation via inter- or intramolecular cyclization and the other involving late-stage functionalization of parent 2 H -chromenes .…”

Gold self-relay catalysis enabling annulative oxygenation of propargylic alcohols with O-nucleophiles

“…10 Moreover, there are also some other important entries to these oxo-heterocycles. 11 Despite these advances, the continuous development of a new synthetic technology for the generation of 2,3-disubstituted benzo[ b ]furan is still in great demand, given its great application in pharmaceutical chemistry and functional materials.…”