Aldehydes singly occupied molecular orbital

In 2007, MacMillan and co-workers reported conceptually novel reactions employing MacMillan s catalyst 5b [39]. This catalyst worked as a singly occupied molecular orbital (SOMO) catalyst in the presence of cerium (IV) ammonium nitrate (CAN) as a single-electron oxidant and the enantioselective a-allylation of aldehydes... 

In 2007, the groups of MacMillan and Sibi almost simultaneously introduced a new mode of organocatalytic activation, termed SOMO (singly occupied molecular orbital) catalysis, which was founded upon the transient production of a 37r-electron radical cation species that could function as a generic platform of induction and reactivity. This new mode of organocatalytic activation, was founded upon the mechanistic hypothesis that one-electron oxidation of a transient enamine intermediate, derived from the aldehyde and the chiral amine catalyst, rendered a 37i -electron SOMO-activated species, which could readily participate in asymmetric bond construction. 

Most of these reactions are accomplished using the singly occupied molecular orbital (SOMO) organocatalytic activation mode [34], The original example is devoted to the intramolecular radical cyclization of aldehydes using some imidazolidinone catalyst under oxidative conditions (Scheme 7.22) [35],... 

Jang, H. -Y., Hong, J. -B., MacMillan, D. W. C. (2007). Enantioselective organocatalytic singly occupied molecular orbital activation the enantioselective a-enolation of aldehydes. Journal of American Chemical Society, 129, 7004-7005. 

SOMO Activation Within the field of aminocatalysis, asymmetric organo-SOMO (singly occupied molecular orbital) catalysis has recently emerged as a powerful technique for the preparation of optically active compounds. In this context, MacMillan and coworkers described in 2008 the formation of y-oxyaldehydes from aldehydes and styrenes by organo-SOMO catalysis [25]. The condensation between the amine catalyst 46 and an aldehyde gave rise to an enamine intermediate, which was then oxidized by ceric ammonium nitrate (CAN) to give a radical cation. Reaction of this radical cation with a nonactivated olefin, namely styrene, led to the... 

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