Metal-catalyzed coupling/carbonylative cyclizations for accessing dibenzodiazepinones: an expedient route to clozapine and other drugs

A sequential strategy to access 10,11-dihydro-5H-dibenzo[b,e][1,4]diazepinones (DBDAPs) is disclosed in this article through a palladium and copper-catalyzed amination (Buchwald-Hartwig (B-H) or Chan-Lam (C-L)) followed by a palladium-catalyzed intramolecular aminocarbonylation with Mo(CO)6 as CO surrogate (to avoid toxic CO handling) of readily available o-phenylenediamines and either 1,2-dibromobenzene or 2-bromophenylboronic acid. The 10,11-dihydro-5H-dibenzo[b,e][1,4]diazepinone could be synthezised in good yield using a sequential catalytic procedure, using both C-L and B-H approaches. Gratifingly, the use of the C-L reaction was more impressive, and afforded the dibenzodiazepinones in good yields (up to 45%; 2 steps) and much milder conditions using copper as the catalyst. The synthetic utility of this novel strategy was showcased by demonstrating a formal synthesis for the antipsychotic drug clozapine and to an anticancer triazole-DBDAP hybrid.

Facile One-Pot Synthesis of Functionalized Quinoline-Fused Fluorescent Dihydro/Spiro-quinazolinone Derivatives

A facile and efficient method has been developed for the synthesis of quinoline-fused fluorescent dihydro/spiro-quinazolinones. A plausible mechanism involving an acid-mediated enaminone intermediate is provided. The reaction proceeded using p-toluene sulfonic acid as a green promoter. The methodology was successful in synthesizing various quinoline-appended spiro-quinazolinones 4a-o. The synthetic utility of compounds 4a-o was demonstrated by synthesizing compounds 6a-d via Suzuki coupling as a key reaction. Significantly, the π-π* electronic transition of compounds 4c and 4k showed a blue shift. The molar extinction coefficient (ε), Stoke's shift (Δu̅), and quantum yield (Φ^f)_c were calculated for these derivatives (4c and 4k).

Ni-Catalysed intramolecular reductive aminocarbonylation of 2-haloaryl-tethered nitroarenes for the synthesis of dibenzazepine-based heterocycles

A nickel-catalysed intramolecular reductive aminocarbonylation of 2-haloaryl-tethered nitroarenes is developed for rapid access to a variety of dibenzoazepinones and their derivatives.

Recent developments in selective N-arylation of azoles

Transition-metal based carbon-heteroatom (C-X) bond formation has attracted the attention of synthetic chemists over the past few years because the resultant aryl/heteroaryl motifs are important substructures in many natural products, pharmaceuticals, etc. Several efficient protocols such as Buchwald-Hartwig amination, Ullmann coupling, Chan-Lam coupling and metal-free approaches have proved beneficial in C-X bond formation. Selective arylation of one hetero-centre over other centres without protection/deprotection thus allowing minimum synthetic manipulation has been achieved for several substrates using these protocols. Azoles are one such novel five-membered heterocyclic core with huge pharmaceutical applications. Though N-arylation on azole-bearing analogues has been extensively practised, selective N-arylation either on one N-centre or the exocyclic N-site of the azole ring in competition with other hetero-centres in the framework has been recently explored for azole-carrying systems. Thus, this review would focus on recent advances in chemo- and regio-selective N-arylation (either on one N-centre or the exocyclic N-site of the azole ring) on azole-containing frameworks.