Identification and optimization of novel pyrimido-isoxazolidine and oxazine as selective hydride donors

Preparation of spiro[indole-3,5′-isoxazoles] via Grignard conjugate addition/spirocyclization sequence

A highly efficient one-pot procedure combining conjugate addition of Grignard reagents to (2-nitroalkenyl)indoles and sub-sequent Brønsted acid-assisted spirocyclization allowed for preparation of 4′H-spiro[indole-3,5′-isoxazoles] in a diastereomerically selective fashion. Utilization of alkyl Grignard reagents provided an easy access to 4′-alkylsubstituted derivatives hardly available by other means.

One-pot procedure combining conjugate addition of Grignard reagents to (2-nitroalkenyl)indoles and subsequent acid-assisted spirocyclization allowed for diastereoselective preparation of 4′H-spiro[indole-3,5′-isoxazoles].

Nitrostyrenes as 1,4-CCNO-dipoles: diastereoselective formal [4+1] cycloaddition of indoles

An unusual reactivity of nitrostyrenes in phosphorous acid was discovered, which permits the employment of these readily available synthons as 1,4-CCNO-dipole surrogates in a highly diastereoselective (4+1)-cycloaddition of indoles to afford 4′H-spiro[indole-3,5′-isoxazoles] in a diastereomerically pure form.

Morita-Baylis-Hillman reaction of acrylamide with isatin derivatives

The Morita–Baylis–Hillman reaction of acrylamide, as an activated alkene, has seen little development due to its low reactivity. We have developed the reaction using isatin derivatives with acrylamide, DABCO as a promoter and phenol as an additive in acetonitrile. The corresponding aza version with acrylate and acrylonitrile has also been developed resulting in high product yields.

Pyrimido[5,4-e]tetrazolo[5,1-b][1,3,4]thiadiazines as a new heterocyclic system

Six novel 2-substituted pyrimido[5,4- e]tetrazolo[5,1- b][1,3,4]thiadiazines were prepared via a multistep synthetic sequence beginning with 5-bromo-2,4-dichloro-6-methylpyrimidine.