Microwave-Promoted Metal-Free α-Alkylation of Ketones with Cycloalkanes through Cross-Coupling of C(sp3)-H Bonds

The microwave-promoted alpha-alkylation of ketones with cycloalkanes as alkylating agents under metal-free conditions is presented. The reaction mechanism involves the DTBP-initiated (DTBP=di-tert-butyl peroxide) microwave-assisted formation of the required cycloalkyl and alpha-ketone carbon radicals followed by a selective cross-coupling step. This is the first example in which simple ketones and 1,3-diketones have been efficiently alkylated with cycloalkanes under metal-free conditions through the cross-dehydrogenative coupling of C(sp(3))-H bonds. Compared with previous methods, this alkylation protocol has advantages such as the use inexpensive and abundant substrates under metal-free conditions and its good atom-economy and sustainability. Moreover, the substituted ketones can be used as intermediates in the preparation of the synthetically and biologically valuable trisubstituted alkenes.