Multicomponent Reactions for the Synthesis of Heterocycles

Multicomponent domino reactions (MDRs) serve as a rapid and efficient tool for the synthesis of versatile heterocycles, particularly those containing structural diversity and complexity, by a one‐pot operation. These reactions can dramatically reduce the generation of chemical wastes, costs of starting materials, and the use of energy and manpower. Moreover, the reaction period can be substantially shortened. This Review covers recent advances on multicomponent domino reactions for the construction of five‐, six‐, and seven‐membered heterocyclic skeletons and their multicyclic derivatives.     

A mild and efficient method for the synthesis of vinylogous carbamates from alkyl azides

A mild and efficient one-pot method for the synthesis of vinylogous carbamates is reported starting from alkyl azides under a hydrogen atmosphere using 10% Pd/C. The resulting products are useful intermediates for the synthesis of heterocyclic compounds, natural products, and in peptidomimetics.     

Enantiospecific synthesis of (−)-d-noviose from (−)-pantolactone

Noviose, the rare sugar moiety present in novobiocin, is an important antimicrobial and antitumor agent that has been shown to inhibit DNA gyrase and HSP90. An enantiospecific synthesis of d-(−)-noviose starting from commercially available (−)-pantolactone is reported.     

Microwave-assisted multicomponent reaction in water leading to highly regioselective formation of benzo[f]azulen-1-ones

Microwave-assisted three-component reaction has been established for the regioselective synthesis of benzo[f]azulen-1-ones. The reaction was performed in aqueous media under microwave irradiation by using readily available and inexpensive starting materials. A total of 38 examples were examined to show a broad substrate scope and good overall yields (70-89%). The present new synthesis shows attractive green chemistry characteristics, such as the use of water as reaction media, concise one-pot conditions, short reaction periods (7-24 min), easy work-up/purification, and reduced waste production without the use of any strong acids or metal promoters.     

An efficient synthesis of 4-substituted coumarin derivatives via a palladium-catalyzed Suzuki cross-coupling reaction

An efficient Pd-catalyzed Suzuki cross-coupling reaction of sterically crowded 4-chlorocoumarin derivatives with air- and moisture-stable potassium organotrifluoroborates is developed. This methodology has been used to generate a series of novel alkyl, aryl, and vinyl substituted coumarin derivatives in good to excellent yields. The twisted conformation of the vinyl groups in the X-ray crystal structures of (2-oxo-4-vinyl-2H-chromen-3-yl)methyl acetate (2) and (2-oxo-4-vinyl-2H-chromen-3-yl)methyl 2,2,2-trichloroacetimidate (3), along with the atropisomerism of 3-(hydroxymethyl)-4-(2-methoxyphenyl)-2H-chromen-2-one (1d), are evidence of the steric crowding in these adducts.