Sequential Oxidative Fragmentation and Skeletal Rearrangement of Peroxides for the Synthesis of Quinazolinone Derivatives

A solvent-free and catalyst-free reaction of o-aminobenzophenone with aryl isothiocyanates: expedient access to congested 4-phenyl-4-hydroxyquinazolin-2-thione derivatives

An efficient method to construct 4-phenyl-4-hydroxyquinazolin-2-thiones 3via solvent-free and catalyst-free addition of o-aminobenzophenone 1 with aryl isothiocyanates 2 under thermal conditions has been developed, providing new congested 4-phenyl-4-hydroxyquinazolin-2-thiones 3 in practically quantitative yields via simple purification by filtration/recrystallization. Extension of these conditions to o-aminoacetophenone 4 in place of o-aminobenzophenone 1 led to 4-methylenequinazoline-thione 5 as a result of a subsequent dehydration reaction.

Hauser-Kraus Annulation Initiated Multi-Cascade Reactions for Facile Access to Functionalized and Fused Oxazepines, Carbazoles and Phenanthridinediones

The Hauser-Kraus (H-K) annulation of N-unsubstituted 3-olefinic oxindoles with 3-nucleophilic phthalides triggers a cascade of ring expansion and ring contraction reactions through several regioselective steps in one pot. While oxazepines were isolated in the presence of stoichiometric amounts of base at room temperature, carbazoles and phenanthridinediones were the products in the presence of excess base and microwave irradiation. Mechanistic studies guided by stepwise reactions and control experiments revealed that the isolable oxazepine intermediate, formed via ring expansion of the H-K adduct, is the key precursor to carbazole and phenanthridinedione via decarboxylative regioselective cyclizations.

Urea-Functionalized Fe4 L6 Cages for Supramolecular Gold Catalyst Encapsulation to Control Substrate Activation Modes

The excellent catalytic performances of enzymes in terms of activity and selectivity are an inspiration for synthetic chemists and this has resulted in the development of synthetic containers for supramolecular catalysis. In such containers the local environment and pre-organization of catalysts and substrates leads to control of the activity and selectivity of the catalyst. Herein we report a supramolecular strategy to encapsulate single catalysts in a urea-functionalized Fe4 L6 cage, which can co-encapsulate a functionalized urea substrate through hydrogen bonding. Distinguished selectivity is obtained, imposed by the cage as site isolation only allows catalysis through π activation of the substrate and as a result the selectivity is independent of catalyst concentration. The encapsulated catalyst is more active than the free analogue, an effect that can be ascribed to transitionstate stabilization rather than substrate pre-organization, as revealed by the MM kinetic data. The simple strategy reported here is expected to be of general use in many reactions, for which the catalyst can be functionalized with a sulfonate group required for encapsulation.