Asymmetric N-H/N-alkyl olefin azirdinations and ring-opening transformations

Rice University, Houston TX

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Abstract

? DESCRIPTION (provided by applicant): Aziridines, the three-membered and equally highly-strained nitrogen analogues of epoxides, are important synthetic intermediates en route to structurally complex molecules due to their versatility in myriad regio- and stereoselective transformations. The aziridine structural motif, predominantly N-H and to a lesser extent N-alkyl, also appears in natural products which exhibit potent antibiotic, immunomodulatory and anticancer properties. Current direct olefin aziridination methods rely either on the transfer of substituted nitrenes to the C=C bond of olefins or the transfer of substituted carbenes to the C=N bond of imines. Normally, the result is an aziridine bearing a strongly electron-withdrawing N-protecting group whose removal can result in destruction of the aziridine. In addition, the high reactivity of these N-protected nitrenes can give rise to non-productive allylic C-H amination as well as the loss of stereospecificity. This proposal has two main goals: (a) the development of direct, stereospecific and practical syntheses of unprotected (i.e., N-H, N-alkyl) aziridines and (b) bis-functionalization of olefins leading to vicinally functionalized amines using homogeneous transition metal catalysis. These objectives will be developed in three specific aims: (1) Development and optimization of the direct, catalytic enantioselective N-H/N-alkyl aziridination of olefins; (2) Development of transition-metal-catalyzed direct hydro-/carbo-/heteroatom-amino olefin difunctionalizations, affording unprotected amino-alcohols, azido-amines as well as primary, secondary and tertiary amines; (3) Design and synthesis of a family of novel N-H/N-alkyl transfer agents (i.e., aminating agents) that will provide an unprecedented range of chemo- and stereo-selectivities in both direct olefin N-H/N-alkyl aziridinations and hydro-/carbo-/heteroatom-amino olefin difunctionalizations.