Rhodium(III)-catalyzed Construction of D-A Type Polyheteroaromatics with Fluorinated Benzothiadiazole as a Modifiable Acceptor Block

An efficient pathway to a new family of fluorinated polyheteroaromatic D-A molecules has been developed. The method is based on the Rh(III)-catalyzed regioselective [4+2]-annulation of N-(pivaloyloxy)-benzamides with 4-ethynyl-5,6-difluoro-7-(p-methoxyphenyl)-2,1,3-benzothiadiazole as a key step followed by the aromatization/Suzuki coupling sequence to furnish the target D-A systems with modifiable acceptor block. The discovered difference in reactivity between ArB(OH)(2) and ArBPin allows performing a divergent modification of BTD acceptor block by the manipulation of aryl boronic reagents in the ortho-selective C-F activation of the fluorinated BTD moiety under Suzuki reaction conditions to furnish new D-1-pi-A-D-2 systems in good yields. Such step-by-step modification of the acceptor block has been achieved by Pd-catalyzed C-F bond activation under isoquinoline ring assistance for the first time.

Automated summary

An efficient pathway to a new family of fluorinated polyheteroaromatic D-A molecules has been developed. This method allows the modification of the acceptor block and provides a good yield of the target D-A systems. The discovery of different reactivity between aryl boronic reagents enables the divergent modification of the BTD acceptor block through ortho-selective C-F activation.