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A new and efficient metal-free tandem acylation/cyclization of alkynoates with aldehydes was developed for the synthesis of 3-acyl-4-arylcoumarins. The reaction was achieved by the addition of acyl radical to alkynes and a C-H bond functionalization to form two new C-C bonds simultaneously.

Ag2CO3-catalyzed difunctionalization of alkynes via a radical phosphonation and C-H functionalization tandem process was developed to synthesize various 3-phosphonated coumarins in moderate to high yields with high regioselectivity. A catalytic amount of cheap and nontoxic silver salt was employed in the domino C-P and C-C formation of alkynoates for the first time. Mechanistic studies indicate that the reaction pathway might proceed via the generation and cyclization of a phosphonated vinyl radical intermediate.

A novel Pd(II)-catalyzed dehydrogenative cross-coupling reaction between coumarins and H-phosphonates has been developed to give the corresponding 3-phosphonated products in moderate to good yields with high selectivity.

Cu-catalyzed CDC reactions of coumarins with cyclic ethers and cycloalkanes were achieved to afford a variety of C-3 functionalized coumarins bearing the C(sp 2 )–C(sp 3 ) bond in moderate to excellent yields. The conversion was proposed to proceed via a radical process. [ABSTRACT FROM AUTHOR]

4-Methylcoumarins yield only trace amounts of product due to steric hindrance. [ABSTRACT FROM AUTHOR]

A novel approach for the preparation of potentially biologically attractive 3-acyl-4-arylcoumarins using readily prepared aryl alkynoates and simple aldehydes as starting materials is developed. [ABSTRACT FROM AUTHOR]

Optimized conditions allow the preparation of a broad spectrum of target compounds bearing different substitution patterns. [ABSTRACT FROM AUTHOR]

The article presents chemical equations related to the article "Regioselective Palladium-Catalyzed Phosphonation of Coumarins with Dialkyl H-Phosphonates via C-H Functionalization" by X. MI and others, which was published in the journal "Organic Letter" in 2013.