Regio- and stereoselective synthesis of tetra- and triarylethenes by N-methylimidodiacetyl boron-directed palladium-catalysed three-component coupling

• DOI: 10.1038/s42004-019-0137-0
• Publication Date: 2019-03-22T11:02:47Z
• Authors: E. Emily Lin; Jia-Qiang Wu; Felix Schäfers; Xiao-Xuan Su; Ke-Feng Wang; Ji-Lin Li; Yunyun Chen; Xin Zhao; Huihui Ti; Qingjiang Li; Tian-Miao Ou; Frank Glorius; Honggen Wang
• Keywords: 01 natural sciences; 0104 chemical sciences

AbstractThe flexible synthesis of tetra- and triarylethenes bearing different aryl groups has been a long-standing challenge in organic synthesis. Here we report a palladium-catalysed syn-diarylation of arylethynyl N-methyliminodiacetyl (MIDA) boronates. The products, triarylalkenyl N-methyliminodiacetyl boronates, allow a step-economic and modular synthesis of tetra- or triarylethenes via a subsequent stereospecific Suzuki-Miyaura coupling reaction or base-promoted protodeborylation, respectively. Use of the sp3-B(MIDA) masked aryl alkyne is the key factor for success by offering an exceptionally good regioselectivity for the boron-retentive coupling. The unusual regioselectivity is believed to arise from the stabilization due to the strong electron donation from the C−Pd σ bond to the p-orbital of boron in the transition state of migratory insertion. A broad range of differently substituted tetra- and triarylethenes are constructed in good yields and geometrical control. Synthetic manipulation of the C-B bond also enables the facile construction of several other types of tetra-substituted alkenes.