Iodonium ylides in organic synthesis.

摘要

My thesis deals with reaction mechanisms and application of iodonium ylides in synthetic organic chemistry. Part I deals with the detailed mechanistic investigation of cycloaddition reactions of iodonium ylides. The mechanisms suggested were either using the carbene mechanism or dipolar addition. In continuation of our earlier studies we initiated a systematic study of iodonium ylide chemistry, using various dipolarophiles under various catalysts to comprehend the precise mechanism of these reactions. Utilizing two different ylides, namely phenyliodonium dimedonide and phenyliodonium dimethyl malonate, we carried out reactions with five different dipolarophiles (CS2, CH3CN, PhNCO, PhNCS) under different catalytic conditions (Rh 2(OAc)4, CuCl, CuCl2, Cu(acac)2). The data from each reaction were compared and it helped elucidate several different mechanisms operating for the various reaction conditions. In addition, we were the first to develop a new class of iodonium ylides, 'heteroaromatic iodonium ylides' and demonstrate their applications using the heteroaryl migration ability of iodonium ylides and for the synthesis of complex heterocyclic molecules.;These mechanistic studies were substantiated with application oriented studies of iodonium ylide chemistry in the efficient synthesis of steroidal compound, CDB-4124. CDB-4124 showed antiprogestin activity with a minimal antiglucocorticoid activity and hence is a very useful and effective drug for the treatment of endometriosis. Using hypervalent iodine chemistry we were able to demonstrate a mode of synthesis of CDB-4124, which is convenient, high yielding and eco-friendly.;Part II of my thesis deals with the synthesis of naturally available prenylated flavonoid, Abyssinone II that has wide application as an aromatase inhibitor and hence prevents the tumor producing activity of estrogen. We report here the first total synthesis and a convenient method for large scale (50g) synthesis of Abyssinone II. Following synthesis, the compound was submitted to the McKesson Bio Services for clinical trials in collaboration with the National Cancer Institute. In addition, two other analogues of Abyssinone II were also synthesized utilizing hypervalent iodine chemistry. The synthetic Abyssinone II and its analogues were also tested for their viral preventing activity against different strains of ocular herpes virus.