Investigations of scope and mechanism of nickel-catalyzed transformations of glycosyl trichloroacetimidates to glycosyl trichloroacetamides and subsequent, atom-economical, one-step conversion to α-urea-glycosides

Rearrangement of Benzylic Trichloroacetimidates to Benzylic Trichloroacetamides

The rearrangement of allylic trichloroacetimidates is a well-known transformation, but the corresponding rearrangement of benzylic trichloroacetimidates has not been explored as a method for the synthesis of benzylic amines. Conditions that provide the trichloroacetamide product from a benzylic trichloroacetimidate in high yield have been developed. Methods were also investigated to transform the trichloroacetamide product directly into the corresponding amine, carbamate, and urea. A cationic mechanism for the rearrangement is implicated by the available data.

Synthesis of a polymerizable, bivalent glycan mimetic of the HIV envelope spike gp120

A synthetic study on the creation of a bivalent, ROMP capable monomer has the ability to be polymerized into the corresponding neo-glycopolymer mimetic of the surface glycans on gp120 envelope spike of the HIV virus. In our approach, we have developed a new strategy for orthogonally attaching both the terminal Manα1-2Man disaccharide unit of the D1 arm of Man9GlcNAc2 of HIV gp120 and the terminal Manα1-2 unit of its D2 arm to a bivalent scaffold to produce the corresponding polymerizable monomer. The Manα1-2 saccharide moieties were assembled using a nickel catalyst, Ni(4-F-PhCN)₄(OTf)₂, to activate trihaloacetimidate donors under mild and operationally simple procedure.

Scalable synthesis of Fmoc-protected GalNAc-threonine amino acid and T(N) antigen via nickel catalysis

The highly α-selective and scalable synthesis of the Fmoc-protected GalNAc-threonine amino acid and TN antigen in gram scale (0.5-1 g) is described. The challenging 1,2-cis-2-amino glycosidic bond is addressed through a coupling of threonine residues with C(2)-N-ortho-(trifluoromethyl)benzylidenamino trihaloacetimidate donors mediated by Ni(4-F-PhCN)4(OTf)2. The desired 1,2-cis-2-amino glycoside was obtained in 66% yield (3.77 g) with α-only selectivity and subsequently transformed into the Fmoc-protected GalNAc-threonine and TN antigen. This operationally simple procedure no longer requires utilization of the commonly used C(2)-azido donors and overcomes many of the limitations associated with the synthesis of 1,2-cis linkage.

Nickel N-heterocyclic carbene-catalyzed cross-coupling reaction of aryl aldehydes with organozinc reagents to produce aryl ketones

The transformation of aromatic aldehydes into aryl ketones by nickel-catalyzed cross-coupling has been developed. This transformation represents an efficient and attractive synthetic utilization of organozinc reagents.