Synthesis of chiral allenes from ynamides through a highly stereoselective Saucy–Marbet rearrangement

Regio- and stereospecific cis-hydrophenoxylation of ynamides with acidic phenols

Herein we describe a self-acid-enabled chemo-, regio-, and stereospecific cis-hydrophenoxylation of ynamides under reagent-free conditions. The presence of a non-polar solvent such as toluene was found to be beneficial to facilitate the rate-limiting proton transfer between phenols and ynamides to form an intimate ion pair, which is followed by a swift nucleophilic attack of the phenolate oxygen on keteniminium, fulfilling the overall hydrofunctionalization event. This protocol is operationally simple and easily scalable, tolerates a wide variety of functional groups, and shows good compatibility with the requirements of modern green chemistry.

Metal-free hydroalkoxylation of ynesulfonamides with alcohols

Efforts for developing a convenient and expeditious method for synthesizing alkoxy-substituted enamides via nucleophilic addition of alcohols to ynesulfonamides are described. This sequence is completely regioselective and highly stereoselective, and leads to the hydroalkoxylation products in high yields under mild reaction conditions.

One-pot synthesis of tetrasubstituted 2-aminofurans via Au(I)-catalyzed cascade reaction of ynamides with propargylic alcohols

One-pot synthesis of fully substituted 2-aminofurans via a Au(I)-catalyzed cascade reaction of ynamides and propargylic alcohol was realized. Hydroalkoxylation of ynamide with propargylic alcohol, Saucy-Marbet rearrangement, and cyclization of the resultant 3,4-dienamide sequentially proceeds in a one-pot reaction under highly mild conditions to give fully substituted 2-aminofurans.

Metal-free hydroalkoxylation of ynesulfonamides with esters

An efficient metal-free hydroalkoxylation reaction of ynesulfonamides with esters under mild conditions is described. Under the catalysis of TMSOTf, various ynesulfonamides are transformed into the corresponding alkoxy-substituted enamides in high yields with complete regioselectivity and high to excellent stereoselectivity.

Stereoselective Synthesis of (2Z)-2,4-Dienamides via NBS-Mediated Allyloxyl Addition-Claisen Rearrangement-Dehydrobromination Cascade Reaction of Ynsulfonamides

An NBS-promoted allyloxyl addition-Claisen rearrangement-dehydrobromination cascade reaction has been developed. More than 20 substituted alkynylsulfonamides were reacted with allyl alcohols to generate (2Z)-2,4-dienamides in moderate to high yields. A mechanistic model has been proposed to account for the overall reaction sequence including the stereochemical outcome. Theoretical calculations suggested that a [3,3] sigmatropic rearrangement be the rate-limiting step.

Copper(II)- and palladium(II)-catalyzed enantioselective Claisen rearrangement of allyloxy- and propargyloxy-indoles to quaternary oxindoles and spirocyclic lactones

In this Article, a strategy to obtain highly enantioselective catalysts for the Claisen rearrangement of allyloxy- and propargyloxy-indoles is outlined. Ultimately, copper BOX and palladium BINAP or PHOX catalysts were discovered as superior in catalyzing Claisen rearrangements of allyloxy- or proparyloxy-substituted indoles to generate oxindoles bearing allyl- or allenyl-substituted quaternary centers. This method proved to be tolerant of a broad range of functional groups. Tandem reactions of the silyl-allene products provide rapid access to a variety of spirocyclic oxindoles in one operation.

Irregularities in the effect of potassium phosphate in ynamide synthesis

The yields of ynamides using Hsung's second generation protocol depend substantially on the quality of K(3)PO(4). Samples of K(3)PO(4) from different suppliers were investigated by various techniques, revealing that the use of pure and anhydrous K(3)PO(4) provides higher ynamide yields in comparison to samples contaminated with hydrates (K(3)PO(4) x 1.5 H(2)O and K(3)PO(4) x 7 H(2)O). With high quality K(3)PO(4), a number of ynamides were synthesized in yields of 52-91%. In addition, we report that ynamides can undergo regioselective hydroamination with carbamates.

Saucy-Marbet Rearrangements of Alkynyl Halides in the Synthesis of Highly Enantiomerically Enriched Allenyl Halides

A stereospecific Saucy-Marbet rearrangement of alkynyl halides is described here. These rearrangements provide an entry to highly enantiomerically enriched allenyl bromides and chlorides through excellent chirality transfer and the reservation of optical integrity of alkynyl halides.

A triazole-templated ring-closing metathesis for constructing novel fused and bridged triazoles

The feasibility of trapping the vinyl copper intermediate generated in situ from azide-[3 + 2] cycloadditions and viability of employing these triazoles as unique templates for ring-closing metathesis are described here; this work effectively combines the two powerful reactions for the first time to construct various de novo fused and bridged triazoles that are otherwise not trivial to synthesize.

Tandem azidination– and hydroazidination–Huisgen [3 + 2] cycloadditions of ynamides. Synthesis of chiral amide-substituted triazoles

Tandem azidination- and hydroazidination-Huisgen [3 + 2] cycloadditions of ynamides are described here. These processes are regioselective and chemoselective, leading to the synthesis of chiral amide-substituted triazoles.