P. L. Fuchs

Mechanistic aspects of the CH alkynylation reaction of acetylenic triflones. Determination of phenyl versus cyclohexyl migratory aptitude for a vinylidine carbene

Abstract 13C-2 labeled phenyl ethynyl triflone undergoes regiospecific CH alkynylation upon reaction with cyclohexane. The 13C label is found to be exclusively adjacent to the phenyl group in the product phenyl cyclohexyl acetylene, consistent with cyclohexyl radical addition at the α-position. Control studies show preferential phenyl migration from a vinylidine carbene, thus excluding the presence of such an intermediate.

Conversion of δ-(sulfonyl)amino-α-epoxy ketones to bicyclic ketopyrroles via intramolecular conjugate-addition to azoene intermediates. Synthesis of the bicyclic ketopyrrole core of the 1-azafulvene roseophllin☆

Abstract Reaction of δ-(sulfonyl)amino-α-epoxy ketones with dimethylhydrazine results in cyclization to pyrrolidine-fused β-hydroxy dimethylhydrazones. Hydrolysis, mesylation, and elimination affords dihydropyrroles which can be converted to sulfonyl-protected ketopyrroles via oxidation with NIS; alternatively, treatment with DBU affords NH bearing ketopyrroles.

Alkynylatlon of aldehydic CH bonds via reaction with acetylenic triflones

Abstract Reaction of aldehydes with acetylenic triflones affords acetylenic ketones and alkylated acetylenes via the intermediacy of acyl radicals, the product ratio being highly dependent upon aldehyde structure and reaction conditions.

Synthesis of a family of epoxyvinyltriflate stereotetrads from 4-hydroxycyclohex-2-en-1-one☆

Abstract 4-Hydroxy cylohex-2-en-1-one can be converted into a family of highly oxygenated cyclohexyl epoxyvinyltriflates by epoxidation, rearrangement, and epoxidation. Furthermore, double stereoselection via Jacobsen epoxidation enables synthesis of compounds such as 20a which were previously very difficult to prepare.

Synthesis of 6-carbon termini-differentiated stereotriads via symchiral 2-trifloxy-1,3-cyclohexadiene monoepoxide

Abstract Jacobsen epoxidation of 2-trifloxy-1,3-cyclohexadiene provides a valuable asymmetric monoepoxide product that can be readily manipulated to efficiently provide highly-functionalized symchiral cyclic and acyclic synthons.

Chromium [II]-mediated reductive cleavage of a tertiary halide bearing three β-alkoxy groups. Synthesis of the north hexacyclic steroid unit of the cephalostatin family

Transformation of aldehyde 4 to 17nat, a hexacyclic steroid bearing the requisite functionality and spiroketal stereochemistry of the North portion of the cephalostatin family is described. The key reaction involves CrCl2 mediated reductive cleavage of a tertiary bromide which is beta to three alkoxy groups.

Use of phosphazene base and phase-transfer conditions for regiospecific alkylative isomerization of vinyl sulfones capable of undergoing β-elimination reactions☆

Abstract Using phosphazene base, P 4 -t-Bu or basic phase-transfer catalyst conditions, vinyl sulfones were regiospecifically alkylated at the α-position. No β-elimination products were observed in a system capable of undergoing anion-promoted β-elimination. The scope and limitations of these reactions were studied.