Studies Of Three-coordinate Phosphorus Reagents Promoted [1 + 4] Annulations Involving 1,2-Dicarbonyl Compounds

The development of highly efficient synthetic methods for cyclic compounds is of great significance in the syntheses of pharmaceutically active molecules,natural products and other functional organic molecules.Recently,nucleophilic three-coordinate phosphorus-mediated annulations,which provide highly efficient access to a variety of carbo-and heterocycles,have attracted extensive research interest from organic chemists due to their merits such as metal-free and mild conditions,the ready availability of starting materials.The Kukhtin-Ramirez adducts,a type of five-coordinate phosphorus compounds that are generated in situ via addition of three-coordinate phosphorus reagents to 1,2-dicarbonyl compounds,possess highly synthetic potential in organic chemistry for they can serve as the carbene surrogates due to their 1,1-dipole structural characteristics.This thesis focuses on exploring the reactivity pattern of Kukhtin-Ramirez adducts generated in situ from three-coordinate phosphorus reagents and 1,2-dicarbonyl compounds as 1,1-dipoles in [1 + 4] annulation reactions,which leads to new synthetic methodologies for important five-membered carbo-and heterocylces.The thesis contains the following two sections:1.The three-coordinate phosphorus reagent-mediated [1 + 4] annulation of isatins with ?,?-unsaturated enones has been investigated.Under optimized conditions,the reaction exhibits a wide substrates scope and good diastereoselectivities,which provides a highly efficient synthetic strategy to pharmaceutically active and naturally occurring spirooxindole-dihydrofurans.Based on experimental results,the reaction is proposed to proceed via a cascade Michael addition-intramolecular SN2 sequence,and represents the first [1 + 4] annulation of Kukhtin-Ramirez adducts acting as 1,1-dipoles.2.A novel three-coordinate phosphorus reagent-mediated [1 + 4] annulation of 1,2-dicarbonyl compounds with 1,1-dicyano-1,3-dienes has been explored,affording new access to cyclopentenimines and cyclopentenones.This annulation exhibits a broad substrates scope.Different kinds of 1,2-dicarbonyl compounds(e.g.isatin derivatives,?-carbonyl esters,?-diketones)and 1,1-dicyano-1,3-dienes with different substituents were all well tolerated.Control experiments indicate that this reaction proceeds through a tandem P(NMe2)3-mediated cyclopropanation/base-catalyzed cyclopropane rearrangement process,and it therefore represents an unprecedented [1 + 4] annulation mode of Kukhtin-Ramirez adducts as 1,1-dipoles.