Defluorinative 1,3-Dienylation of Fluoroalkyl N-Triftosylhydrazones with Homoallenols.

A silver-catalyzed regioselective defluorinative 1,3-dienylation of trifluoromethyl phenyl N-triftosylhydrazones using homoallenols as 1,3-dienyl sources provides a variety of α-(di)fluoro-ß-vinyl allyl ketones with excellent functional group tolerance in moderate to good yields. The reaction proceeds through a silver carbene-initiated sequential etherification and Claisen type [3,3]-sigmatropic rearrangement cascade. The synthetic utility of this protocol was demonstrated through the downstream synthetic elaboration toward diverse synthetically useful building blocks.

Transition-metal-free azide insertion of N-triftosylhydrazones using a non-metallic azide source.

Benzylic azides, an important class of active organic synthons, were synthesized in high yields from the easily accessible N-triftosylhydrazones with stable TMSN3 under mild conditions. The reaction features high efficiency and excellent functional group tolerance, as illustrated by gram-scale synthesis and the synthesis of drug-like molecules. Mechanistic studies reveal that azidation occurs at the electron-deficient diazo-carbon via the elimination of N2 by an azide ion.

Domino process in silver-catalyzed reactions of N-arylformimidates and active methylene compounds involving cycloisomerization and 1,3-alkenyl shift.

We have developed an efficient method for the synthesis of 2,3-disubstituted indoles from alkyne iminoethers 1 that employs a domino process involving Ag-catalyzed condensation followed by a tandem Ag-induced cycloisomerization and 1,3-alkenyl shift to Ag-activated carbon. This methodology can be useful in regioselectively constructing 3-alkylated indoles, which are part of the structures of biologically active compounds and important alkaloids.

Au(I)-catalyzed hydrative rearrangement of 1,1-diethynylcarbinol acetates to functionalized cyclopentenones and allenones.

Atom-economical syntheses of isomeric 5-acetoxy-2-alkyl-2-cyclopentenones (2) and acetoxymethyl alpha-alkylallenones (3) have been described via Au-catalyzed hydrative rearrangement of 1,1-diethynylcarbinol acetates (1). In anhydrous condition, Au(I)-catalyzed [3,3]-rearrangement of 1 afforded the 3-alkynylallenyl acetate 4 in low yield. Treatment of 1 with Au(I) catalyst in wet CH(2)Cl(2) produced either 2 or 3 as a major product depending on the temperature, reaction time, and catalyst loading. D has been proposed as an intermediate, which might be formed via Au(I)-induced internal oxacyclization of the intermediate 4 followed by chemoselective nucleophilic attack by the water molecule. Formation of 2 or 3 might be explained via sequential 1,3-dioxole ring opening and gold-promoted 5-endo-dig carbocyclization or simple protonation of the intermediate D, respectively.

Ag(I)-Catalyzed Domino Cyclization-Addition Sequence with Simultaneous Carbonyl and Alkyne Activation as a Route to 2,2'-Disubstituted Bisindolylarylmethanes.

An efficient synthesis of symmetrical 3, 3'-bisindolylarylmethanes with various substituents on the indole moiety has been developed by Ag(I)-catalyzed cycloisomerization and an deoxygenative addition sequence on o-alkynylanilines and aryl aldehydes. Ag(I) is proposed to activate alkyne unit and carbonyl moiety simultaneously leading to a domino first 5-endo-dig indole annulation, addition to C═O, second indole annulation, and its dehydroxylative addition.