Stereoselective Alkylation of (S)-N-Acyl-4-isopropyl-1,3-thiazolidine-2-thiones Catalyzed by (Me3P)2NiCl2

Stereoselective Alkylation of Chiral Titanium(IV) Enolates with tert-Butyl Peresters

Here, we present a new stereoselective alkylation of titanium(IV) enolates of chiral N-acyl oxazolidinones with tert-butyl peresters from Cα-branched aliphatic carboxylic acids, which proceeds through the decarboxylation of the peresters and the subsequent formation of alkyl radicals to produce the alkylated adducts with an excellent diastereoselectivity. Theoretical calculations account for the observed reactivity and the outstanding stereocontrol. Importantly, the resultant compounds can be easily converted into ligands for asymmetric and catalytic transformations.

Direct and Enantioselective Aldol Reactions Catalyzed by Chiral Nickel(II) Complexes

A direct and asymmetric aldol reaction of N‐acyl thiazinanethiones with aromatic aldehydes catalyzed by chiral nickel(II) complexes is reported. The reaction gives the corresponding O‐TIPS‐protected anti‐aldol adducts in high yields and with remarkable stereocontrol and atom economy. Furthermore, the straightforward removal of the achiral scaffold provides enantiomerically pure intermediates of synthetic interest, which involve precursors for anti‐α‐amino‐β‐hydroxy and α,β‐dihydroxy carboxylic derivatives. Theoretical calculations explain the observed high stereocontrol.

Direct and Asymmetric Nickel(II)-Catalyzed Construction of Carbon-Carbon Bonds from N-Acyl Thiazinanethiones

A wide array of new N-acyl thiazinanethiones are employed in a number of direct and enantioselective carbon-carbon-bond-forming reactions catalyzed by nickel(II) complexes. The electrophilic species are mostly prepared in situ from ortho esters, methyl ethers, acetals, and ketals, which makes the overall process highly efficient and experimentally straightforward. Theoretical calculations indicate that the reactions proceed through an open transition state in a S_N1-like mechanism. The utility of this novel procedure has been demonstrated by the asymmetric preparation of synthetically useful intermediates and the total synthesis of peperomin D.

Stereoselective and Catalytic Synthesis of anti-β-Alkoxy-α-azido Carboxylic Derivatives

Direct addition of a chiral N-azidoacetyl thiazolidinethione to a variety of dialkyl acetals catalyzed by a commercially available and structurally simple nickel(II) complex gives access in good yields and a highly stereocontrolled manner to anti-β-alkoxy-α-azido carboxylic derivatives which, in turn, can be easily converted into a wide array of enantiomerically pure compounds.

Diastereoselective and Catalytic α-Alkylation of Chiral N-Acyl Thiazolidinethiones with Stable Carbocationic Salts

Direct nickel-catalyzed alkylation of chiral N-acyl-4-isopropyl-1,3-thiazolidine-2-thiones using a commercially available nickel(II) complex, (Me₃P)₂NiCl₂, has been developed for tropylium and trityl tetrafluoroborate salts. The reaction provides a single diastereomer of the corresponding adducts in good to high yields, which, in turn, can be easily converted into a wide array of enantiomerically pure compounds that are difficult to obtain by other asymmetric procedures.

Stereoselective Synthesis of the C9-C19 Fragment of Peloruside A

A concise synthesis of the C9-C19 fragment of peloruside A that is both highly stereoselective and efficient is described. Achieving an overall yield of 23% over 14 steps, this synthesis not only is high yielding but also involves four chromatography steps. This approach is based on the addition of metal enolates of chiral auxiliary scaffolds generated by either catalytic or stoichiometric amounts of nickel(II) or titanium(IV) Lewis acids.

Synthesis of functionalized 5-substituted thiazolidine-2-thiones via adscititious xanthate-promoted radical cyclization of allyl(alkyl/aryl)dithiocarbamates

An adscititious radical precursor-promoted cyclization is designed and realized in efficient synthesis of functionalized 5-substituted thiazolidine-2-thiones from alkyl allyl(alkyl/aryl)dithiocarbamates.