Employing a chiroptical sensor for the absolute stereochemical determination of α-amino and α-hydroxyphosphonates.

The absolute stereochemistry of the α-amino and α-hydroxyphosphonates is determined using a chiroptical sensor. The induced helicity of the host-guest complex is correlated to the chirality of the guest molecule a simple binding model. The relative size of the substituents dictates the predominant helical population, leading to an easy circular dichroic readout.

Zirconium-catalyzed asymmetric Kabachnik-Fields reactions of aromatic and aliphatic aldehydes.

An effective catalyst has been developed for the three-component reaction of aldehydes, anilines and phosphites in an asymmetric catalytic Kabachnik-Fields reaction to give α-aminophosphonates. A catalyst was sought that would give high asymmetric inductions for aromatic and, and more particularly, for aliphatic aldehydes since there has not previously been an effective catalyst developed for this class of aldehydes. The optimal catalyst is prepared from three equivalents of the 7,7'-di--butylVANOL ligand, one equivalent of -methylimidazole and one equivalent of zirconium tetraisopropoxide.

Catalyst-Controlled Multicomponent Aziridination of Chiral Aldehydes.

A highly diastereoselective and enantioselective method for the multicomponent aziridination of chiral aldehydes has been developed with BOROX catalysts of the VANOL (3,3'-diphenyl-2,2'-bi-1-naphthol) and VAPOL (2,2'-diphenyl-(4-biphenanthrol)) ligands. Very high to perfect catalyst control is observed with most all substrates examined including aldehydes with chiral centers in the α- and β-positions. High catalyst control was also observed for a number of chiral heterocyclic aldehydes allowing for the preparation of epoxy aziridines, bis(aziridines) and ethylene diaziridines.

Nickel-Catalyzed Reductive Couplings.

The Ni-catalyzed reductive coupling of alkyl/aryl with other electrophiles has evolved to be an important protocol for the construction of C-C bonds. This chapter first emphasizes the recent progress on the Ni-catalyzed alkylation, arylation/vinylation, and acylation of alkyl electrophiles. A brief overview of CO2 fixation is also addressed.

Ni-catalyzed reductive addition of alkyl halides to isocyanides.

This paper highlights Ni-catalyzed reductive trapping of secondary and tertiary alkyl radicals with both electron-rich and electron-deficient aryl isocyanides using zinc as the terminal reductant, affording 6-alkylated phenanthridine in good yields. The employment of carbene ligands necessitates the alkyl radical process, and represents the first utility in the Ni-catalyzed reductive conditions for the generation of unactivated alkyl radicals from the halide precursors.

Catalytic asymmetric synthesis of alkynyl aziridines: both enantiomers of cis-aziridines from one enantiomer of the catalyst.

Alkynyl aziridines can be obtained from the catalytic asymmetric aziridination (AZ reaction) of alkynyl imines with diazo compounds in high yields and high asymmetric inductions mediated by a chiral boroxinate or BOROX catalyst. In contrast to the AZ reaction with aryl- and alkyl-substituted imines, alkynyl imines react to give cis-substituted aziridines with both diazo esters and diazo acetamides. Remarkably, however, the two diazo compounds give different enantiomers of the cis-aziridine from the same enantiomer of the catalyst.

Ni-catalyzed reductive allylation of unactivated alkyl halides with allylic carbonates.

Game of two electrophiles: Two partially positively charged sp(3) carbon atoms can be connected by using a catalytic Ni species in the presence of an environmentally benign Zn reductant, delivering allylated alkanes. This unprecedented approach allowed a variety of unactivated alkyl halides and substituted allylic carbonates to regioselectively afford E-alkenes in good to excellent yields.