%0 Generic
%9 Doctoral Dissertation
%A Sarkar, Nihar Ranjan
%D 2010
%F pittir:9680
%K  N-HETEROCYCLES; ORGANIC SYNTHESIS; IMINIUM ION; PIPERIDINE
%T ALKENYL IMINIUM ION IN DIELS-ALDER REACTION: SYNTHESIS OF HIGHLY SUBSTITUTED N-HETEROCYCLES
%U http://d-scholarship-dev.library.pitt.edu/9680/
%X Heterocyclic structures are critical components of an extensive collection of chemotherapeutic agents, either in service or under development, for treating numerous human illnesses. As a result, reaction technologies for heterocycle construction, in the context of both target- and diversity-oriented synthesis, enjoy a particularly prominent role in medicinal chemistry. Amongst all the C-C bond forming reactions, the classic Diels-Alder cycloaddition remains one of the most powerful transformations in organic chemistry especially for the formation of heterocyclic structures. Herein, we report a new methodology based on inverse electron demand Diels-Alder reaction utilizing reactive "N-alkenyl iminium ion" and a suitable dienophile for the stereoselective synthesis of substituted piperidine derivatives. In presence of a suitable Lewis acid, the "N-alkenyl iminium ion" is generated from the respective enamine-aminal derivative in situ and undergoes Diels-Alder reaction with a dienophile producing a highly substituted N-heterocycle (piperidine derivative) in one step.An efficient transition metal catalyzed isomerization technique for the synthesis of a new enamine-aminal synthon from respective N-allylamine derivatives has been developed. Cationic Ir-(COE) complex, a potential catalyst for ICR chemistry, was used for the isomerization of tosyl protected N-allylamine derivatives to synthesize N-tosyl-alkenyl iminium ion precursor in high geometrical selectivity and quantitative yield whereas carbamate (or amide) protected N-allylamine derivatives were isomerized with good E/Z ratio using Grubbs II.