Anion radical [2 + 2] cycloaddition as a mechanistic probe: stoichiometry- and concentration-dependent partitioning of electron-transfer and alkylation pathways in the reaction of the Gilman reagent Me2CuLi.LiI with bis(enones).

Exposure of easily reduced aromatic bis(enones) 1a-1e to the methyl Gilman reagent Me(2)CuLi.LiI at 0 degrees C in tetrahydrofuran solvent provides the products of tandem conjugate addition-Michael cyclization, 2a-2e, along with the products of [2 + 2] cycloaddition, 3a-3e. Complete partitioning of the Gilman alkylation and [2 + 2] cycloaddition pathways may be achieved by adjusting the loading of the Gilman reagent, the rate of addition of the Gilman reagent, and the concentration of the reaction mixture.

Copper-catalyzed tandem conjugate addition-electrophilic trapping: ketones, esters, and nitriles as terminal electrophiles.

Exposure of enone substrates 1a-18a, which possess appendant ketone, ester, and nitrile moieties, to Et2Zn in the presence of catalytic Cu(OTf)2/P(OEt)3 provides the cyclized products in good to excellent yields and diastereoselectivities. These results represent the first use of ketones, esters, and nitriles as terminal electrophiles in Cu-catalyzed conjugate addition-electrophilic trapping.

Diastereo- and enantioselective catalytic carbometallative aldol cycloreduction: tandem conjugate addition-aldol cyclization.

A catalytic diastereo- and enantioselective method for tandem conjugate addition-aldol cyclization is described. This methodology enables the formation of five- and six-membered ring products from aromatic and aliphatic mono-enone mono-ketone precursors. Notably, in a single manipulation, three contiguous stereogenic centers are created with high levels of relative and absolute stereocontrol.

Studies on the enantioselective catalysis of photochemically promoted transformations: "sensitizing receptors" as chiral catalysts.

A strategy for the enantioselective catalysis of photomediated reactions in solution is described, involving the use of chiral molecular receptors possessing appendant triplet-sensitizing moieties. Energy transfer is selectively directed to bound substrate as a consequence of the distance dependence of triplet-triplet energy transfer. This effect, which is equivalent to a binding-induced rate enhancement, enables substoichiometric chirality transfer from the receptor template to the substrate, as observed in the intramolecular enone-olefin photo[2 + 2]cycloaddition of a quinolone substrate.

Borane-mediated aldol cycloreduction of monoenone monoketones: diastereoselective formation of quaternary centers.

Exposure of monoenone monoketones to catecholborane in THF at ambient temperature results in tandem 1,4-reduction-aldol cyclization. For aromatic and heteroaromatic enones, six-membered cyclic aldol products are formed in excellent yield with high levels of syn diastereoselectivity. Five-membered ring formation proceeds less readily, but the yield of cyclized product is improved through introduction of Rh(I) salts.