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A novel methodology for the annulation of terminal alkynes and o -phenylenediamines by using a combination of a cobalt catalyst and oxygen as a terminal oxidant is reported. This method shows wide substrate scope and good functional group tolerance and provides a wide range of quinoxalines in good to high yields. The method is demonstrated by its gram-scale and broad potential applications. Furthermore, this protocol serves as a powerful tool for the late-stage functionalization of various complex bioactive molecules and drugs to provide a new class of molecules containing two distinct bioactive molecules directly linked. Detailed mechanistic studies reveal that the current reaction goes through a novel mechanism different from the previously reported glyoxal mechanism.

The annulation of heteroaromatic β-halo-α,β-unsaturated carboxylic acids with alkynes proceeds efficiently in the presence of Cu(OAc)2·H2O as a catalyst to afford the corresponding indolo[2,3-c]pyrane-1-ones and thieno[2,3-c]pyrane-7-ones in moderate to good yields. This strategy offers a simple and efficient route for the synthesis of indolo[2,3-c]pyrane-1-ones and thieno[2,3-c]pyrane-7-ones with good tolerance to a variety of functional groups from easily available heteroaromatic β-halo-α,β-unsaturated carboxylic acids.

The addition of o-halobenzoic acids to active internal alkynes proceeds efficiently in the presence of CuCl(2) as a catalyst to give the corresponding isocoumarin derivatives in moderate to good yields. This strategy offers a simple, efficient route to synthesis of the isocoumarin derivatives.

The presence of an acid was found to be essential in the rhodium-catalyzed asymmetric addition of terminal alkynes to diarylphosphinylallenes giving exo-enynes in high yields with high regio- and enantioselectivity. The stereochemical outcome is determined at the protonolysis of the pi-allylrhodium(I) intermediate involved in the catalytic cycle.

A cobalt‐catalyzed annulation of o‐phenylenediamines and internal alkynes for the synthesis of quinoxalines is developed. This method provides a variety of quinoxalines in good to high yields under a simple and mild reaction conditions with molecular O2 as a terminal oxidant. Preliminary mechanistic studies show that a novel reaction mechanism is involved in the current reaction, which is different from the previous reported dicarbonyl compound mechanism via the oxidation of the alkyne. [ABSTRACT FROM AUTHOR]

The synthesis of N-heterocycles of quinoxalines has been developed by an efficient protocol of one-pot annulation of alkynes with o-phenylenediamines. A variety of quinoxalines were prepared in good to high yields in the presence of catalytic amount of iodine as a catalyst. [ABSTRACT FROM AUTHOR]

Abstract: Asymmetric addition of terminal alkynes to allenyl aldehydes took place in the presence of an acetylacetonate complex [Rh(acac)L∗] (L∗=binap or segphos) as a catalyst to give indanol derivatives in high yields with high regio- and enantioselectivity. The acetylacetonate (acac) ligand on the rhodium is important for the selective formation of the indanol derivatives. [ABSTRACT FROM AUTHOR]

The method provides a simple and efficient approach to various 3,4-disubstituted isocoumarins which are of biological interest. [ABSTRACT FROM AUTHOR]

The direct oxidation of internal alkynes proceeds efficiently in the presence of CuI as a catalyst to afford the corresponding 1,2-diketones in good yields. This strategy offers a simple and efficient route for the synthesis of 1,2-diketones from an inexpensive copper catalyst and easily available internal alkynes. The advantage of present protocol is further demonstrated by the synthesis of quinoxaline derivatives from alkynes and 1,2-diaminobenzene via one-pot procedure. [ABSTRACT FROM AUTHOR]

The efficient title reaction uses catalytic amounts of an inexpensive copper catalyst and shows a good functional group tolerance of aryl alkynes. [ABSTRACT FROM AUTHOR]