Publications (7)45.4 Total impact
- [Show abstract] [Hide abstract] ABSTRACT: An efficient method for the phosphine-catalyzed [3+2] cycloaddition reaction of azomethine imines with diphenylsulfonyl alkenes to give dinitrogen-fused bi- or tricyclic heterocyclic compounds in high yields has been described. Moreover, two phenylsulfonyl groups installed on the heterocyclic products could be conveniently removed or transformed to other functional groups, making the reaction more useful. Simplicity is best: Phosphine-catalyzed [3+2] cycloaddition of azomethine imines and phenylsulfonyl alkenes was accomplished. The reactions are operationally simple and proceed smoothly under mild reaction conditions, affording various 1,2-dinitrogen-containing heterocycles in moderate to excellent yields (see scheme).
- [Show abstract] [Hide abstract] ABSTRACT: The first metal-catalyzed [6+3] cycloaddition of tropone with azomethine ylides has been developed. By using a chiral ferrocenylphosphine-copper (I) complex as the catalyst, the asymmetric variant of the [6+3] cycloaddition has also been successfully achieved. The reactions proceeded smoothly under mild conditions, affording piperidine-fused bi-cyclic heterocycles in moderate to high yields with good to excellent diastereo- and enantioselectivies. The procedures are operationally simple and the catalysts are cheap and readily accessible, thus providing a practical approach to piperidine-fused bicyclic heterocycles.
- [Show abstract] [Hide abstract] ABSTRACT: The more dipoles, the merrier: An asymmetric [3+3] cycloaddition of azomethine ylides derived from imines 1 with azomethine imines 2 in the presence of a chiral ferrocenylphosphine-copper catalyst afforded highly functionalized heterocyclic products 3 in high yield with excellent enantio- and diastereoselectivity (see scheme; DBU=1,8-diazabicyclo[5.4.0]undec-7-ene). The 1,3-dipolar reaction partners can be prepared readily from aldehydes.
- [Show abstract] [Hide abstract] ABSTRACT: The process affords dinitrogen-fused tricyclic heterocyclic systems with good to excellent yields, but only poor diastereoselectivities.
- [Show abstract] [Hide abstract] ABSTRACT: The unsaturated ester (I) is reduced completely diastereoselectively to yield the trans-isomers (II).
- [Show abstract] [Hide abstract] ABSTRACT: The thermal [3+2] cycloadditions of two classes of aromatic azomethine imines with allenoates have been investigated. The reactions are operationally simple and proceed smoothly under mild reaction conditions to provide a variety of dinitrogen-fused heterocycles in moderate to excellent yields.
- [Show abstract] [Hide abstract] ABSTRACT: In this paper we describe the phosphine-catalyzed [3 + 2], [3 + 3], [4 + 3], and [3 + 2 + 3] annulations of azomethine imines and allenoates. These processes mark the first use of azomethine imines in nucleophilic phosphine catalysis, producing dinitrogen-fused heterocycles, including tetrahydropyrazolo-pyrazolones, -pyridazinones, -diazepinones, and -diazocinones. Counting the two different reaction modes in the [3 + 3] cyclizations, there are five distinct reaction pathways-the choice of which depends on the structure and chemical properties of the allenoate. All reactions are operationally simple and proceed smoothly under mild reaction conditions, affording a broad range of 1,2-dinitrogen-containing heterocycles in moderate to excellent yields. A zwitterionic intermediate formed from a phosphine and two molecules of ethyl 2,3-butadienoate acted as a 1,5-dipole in the annulations of azomethine imines, leading to the [3 + 2 + 3] tetrahydropyrazolo-diazocinone products. The incorporation of two molecules of an allenoate into an eight-membered-ring product represents a new application of this versatile class of molecules in nucleophilic phosphine catalysis. The salient features of this protocol--the facile access to a diverse range of nitrogen-containing heterocycles and the simple preparation of azomethine imine substrates--suggest that it might find extensive applications in heterocycle synthesis.