Alkali-amide-catalyzed divergent sp2 and sp3 C-H bonds alkylation of alkylthiophenes with alkenes

The divergent transformations of different C-H bonds in a given substrate represent the state of the art in C-H functionalization reactions, wherein there is a need for precise control of the selectivity of the catalyst. Simply by using alkali amide catalysts, we herein selectively achieved the addition of divergent sp(2) and sp(3) C-H bonds of alkylthiophenes to alkenes. Lithium diisopropylamide (LDA) underwent the deprotonation of the C5 sp(2) C-H bond and addition to alkenes to afford C5 alkylation products. Potassium bis(trimethylsilyl) amide (KHMDS) failed to undergo the deprotonation but established a deprotonative equilibrium between the C5 sp(2) C-H bond and the benzylic sp(3) C-H bonds. Further alkylation with alkenes, however, selectively took place at the benzylic sp(3) C-H bond. This work presents the divergent alkylation products of alkylthiophenes, and demonstrates the interesting and distinct behaviors of potassium and lithium amides.