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

The microwave‐promoted α‐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 α‐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(sp3)−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. Rising to the challenge: The microwave‐promoted α‐alkylation of ketones with cycloalkanes as alkylating agents under metal‐free conditions is presented. This selective cross‐coupling of different carbon radicals is a challenge because of the inherent instability and reactivity of these intermediates. The cross‐coupling of C(sp3)−H bonds described herein provides a successful example of the realization of this difficult task.