Development of polyvalent organoiodine reagents for transition metal catalyzed atom and group transfer.

摘要

Primary oxo and nitrene precursors, PhIO and PhINTs, are commonly employed in transition metal catalyzed aziridination and epoxidation reactions. Extensive intermolecular IO and IN secondary bonding render these reagents polymeric and afford heterogeneous reaction conditions. Mechanistic details of oxidations involving these materials are currently lacking due in most part to their insolubility. This research project was initiated to develop polyvalent organoiodine based oxidants that afford homogeneous reaction conditions to assist in the mechanistic investigations of transition metal catalyzed oxo and nitrene transfer reactions.; PhINTs was fully solubilized in organic media by employing external dipolar additives such as organic N-oxides, however, the additives inhibited the nitrene transfer reaction. Soluble analogues of PhIO and PhINTs were sought to be prepared by incorporating dipolar groups such as R₂PO, R₂ NO and RSO₂ internally so as to provide intramolecular IO secondary bonding in lieu of intermolecular IO secondary bonding. Such an intramolecular interaction between the phosphoryl oxygen and iodine center was indicated in the crystal structure of (ortho-iodylphenyl)diphenylphosphine oxide (4h). The chemistry of the first generation soluble iodanes (2-(tert-butylsulfonyl)-( para-toluenesulfonyliminoiodo)benzene (4a) and 2-( tert-butylsulfonyl)-iodosylbenzene) (4b), was explored under various catalytic conditions. The potential for the synthesis of chiral iodanes incorporating the sulfoximine (RSO(NH)-) group was also explored.; The second generation soluble iodanes were obtained by the synthesis of 2-(tert-butylsulfonyl)-5-tert-butyl-(para-toluenesulfonyliminoiodo)benzene (7b) and 2-(tert-butylsulfonyl)-5-tert -butyl-iodosylbenzene (7c). These iodanes displayed 10 fold solubility over 4a and 4b and were evaluated to serve as effective primary oxo and nitrene precursors under manganese and copper catalysis. Photochemical studies of these iodanes were conducted and revealed the aziridination of terminal olefins upon photolysis of 7b . Pairwise competition experiments using various para-substituted styrenes and 7b under photochemical conditions enabled Hammett correlation of the photoaziridination reaction.; The first example of an iodylarene, an organoiodine(V) compound that is soluble in non-aqueous media under ambient conditions was obtained by the synthesis of 2-(tert-butylsulfonyl)-5-tert-butyl-iodylbenzene (7d). 2-(tert-Butylsulfonyl)-5-tert -butyl-iodylbenzene was assessed to be an effective oxo donor under manganese catalysis. The scope for full exploitation of the oxidizing potential of this class of oxidants has been furthered by the synthesis of 7d .