Stepwise Suzuki−Miyaura Cross‐Coupling of Triborylalkenes Derived from Alkynyl−B(dan)s: Regioselective and Flexible Synthesis of Tetrasubstituted Alkenes
Tomohiro Tani, N. Takahashi, Yuuki Sawatsugawa, Mana Osano, Teruhisa Tsuchimoto
Abstract
Abstract Alkenes with three boryl groups of differing reactivities were synthesized and subsequently cross‐coupled regioselectively with aryl halides in a stepwise manner to afford tetrasubstituted alkenes. The key triborylalkene is derived from the platinum‐catalyzed diboration of alkynyl−B(dan)s with B 2 (pin) 2 . Due to excellent regioselectivity and reaction efficiency of each step starting with alkynyl−B(dan)s, tetrasubstituted alkenes with desired carbon frameworks at desired positions can be prepared in high yields. For example, an alkene with four distinct aryl groups, p ‐MeOC 6 H 4 , p ‐CF 3 C 6 H 4 , p ‐MeC 6 H 4 , and p ‐NCC 6 H 4 , was obtained in 71% overall yield via six steps, starting with the dehydrogenative borylation of p ‐MeC 6 H 4 C≡CH with HB(dan). Moreover, a variety of tetrasubstituted alkenes, including regio‐ and stereoisomers of the above tetraarylalkene, AIE‐active TPTPE and derivatives thereof, and ( Z )‐tamoxifen, a well‐known breast cancer drug, were accessed via the developed strategy. magnified image