Benzannulation via the reaction of ynamides and vinylketenes. application to the synthesis of highly substituted indoles.

A two-stage "tandem strategy" for the synthesis of indoles with a high level of substitution on the six-membered ring is described. Benzannulation based on the reaction of cyclobutenones with ynamides proceeds via a cascade of four pericyclic reactions to produce multiply substituted aniline derivatives in which the position ortho to the nitrogen can bear a wide range of functionalized substituents. In the second stage of the tandem strategy, highly substituted indoles are generated via acid-, base-, and palladium-catalyzed cyclization and annulation processes.

Batch and flow photochemical benzannulations based on the reaction of ynamides and diazo ketones. Application to the synthesis of polycyclic aromatic and heteroaromatic compounds.

Highly substituted polycyclic aromatic and heteroaromatic compounds are produced via a two-stage tandem benzannulation/cyclization strategy. The initial benzannulation step proceeds via a pericyclic cascade mechanism triggered by thermal or photochemical Wolff rearrangement of a diazo ketone. The photochemical process can be performed using a continuous flow reactor which facilitates carrying out reactions on a large scale and minimizes the time required for photolysis. Carbomethoxy ynamides as well as more ketenophilic bis-silyl ynamines and N-sulfonyl and N-phosphoryl ynamides serve as the reaction partner in the benzannulation step. In the second stage of the strategy, RCM generates benzofused nitrogen heterocycles, and various heterocyclization processes furnish highly substituted and polycyclic indoles of types that were not available by using the previous cyclobutenone-based version of the tandem strategy.

[2+2] Cycloaddition of ketenes with ynamides. A general method for the synthesis of 3-aminocyclobutenone derivatives.

Ynamides react with ketenes in [2+2] cycloadditions leading to a variety of substituted 3-aminocyclobut-2-en-1-ones. The ynamides employed in these reactions are readily available via the copper-promoted N-alkynylation of carbamates and sulfonamides with alkynyl bromides and iodides. The scope of the [2+2] cycloaddition with regard to both the ketene and ynamide component is described.

Enantioselective alpha-amination of 1,3-dicarbonyl compounds using squaramide derivatives as hydrogen bonding catalysts.

Catalytic enantioselective alpha-hydrazination of 1,3-dicarbonyl compounds with azodicarboxylates was investigated in the presence of our newly developed hydrogen bonding catalyst, squaramide 3j. High yields and high enantioselectivities were achieved with low catalyst loading under mild conditions.