3-Boryl-2,1-borazaronaphthalene: Umpolung Reagents for Diversifying Naphthalene Isosteres

Abstract

A Pd-catalyzed Miyaura borylation of 3-bromo-2,1-borazaronaphthalenes is reported. This method allows the formation of umpolung reagents for subsequent Pd-mediated cross-coupling. Coupling of this nucleophilic partner with a variety of commercially available aryl- and heteroaryl halides allows facile and rapid diversification of these cores.

Unsymmetrical 1,1-Bisboryl Species: Valuable Building Blocks in Synthesis

“…Later, they also utilized the bis-boryl compounds 62a and 63d for a palladium-catalyzed crosscoupling strategy with a variety of aryl halides containing an electron-withdrawing group or an electron-donating group, which yielded the corresponding coupling products 64a-h (Scheme 26). [43]. In 2018, the Molander group reported the borylation of 3-bromo-2,1-borazaronaphthalenes (61) with boronic acid pinacol esters, affording 3-boryl-2,1-borazaronaphthalene 62a-f (1,1-unsymmetrical bis(boryl)alkenes) [43].…”

“…Next, compound 62 was converted into organotrifluroborate salt (63) by treating it with commercially available KHF 2 as a fluoride ion source (Scheme 25B). In 2018, the Molander group reported the borylation of 3-bromo-2,1-borazaronaphthalenes (61) with boronic acid pinacol esters, affording 3-boryl-2,1-borazaronaphthalene 62a-f (1,1unsymmetrical bis(boryl)alkenes) [43]. These borazaronaphthalenes (62) also exhibited an umpolung character in cross-coupling reactions.…”

“…Later, they also utilized the bis-boryl compounds 62a and 63d for a palladium-catalyzed crosscoupling strategy with a variety of aryl halides containing an electron-withdrawing group or an electron-donating group, which yielded the corresponding coupling products 64a-h (Scheme 26). [43]. Later, they also utilized the bis-boryl compounds 62a and 63d for a palladium-catalyzed cross-coupling strategy with a variety of aryl halides containing an electron-withdrawing group or an electron-donating group, which yielded the corresponding coupling products 64a-h (Scheme 26) [43].…”

“…[43]. Later, they also utilized the bis-boryl compounds 62a and 63d for a palladium-catalyzed cross-coupling strategy with a variety of aryl halides containing an electron-withdrawing group or an electron-donating group, which yielded the corresponding coupling products 64a-h (Scheme 26) [43]. In 2014, the Nishihara research group reported the platinum-catalyzed diborylation of 1phenylethynyl MIDA boronate 65a with bis(pinacolato)diboron, affording stereoselective 1,1,2triboryl-2-phenylethene 66a with an 86% yield [44].…”

Late-stage functionalization of BN-heterocycles

“…C3-Boron pinacol ester 59a (Scheme 34a) and C3-BF 3 K salt 60d (Scheme 34b) readily undergo Suzuki cross-coupling reactions. 29 Molander et al also developed a method for C3 functionalization via Suzuki cross-coupling where the BN-naphthalene contains both the nucleophile and the electrophile. 32 This selfarylation occurs when a B-aryl, C3-bromo 1,2-BN-naphthalene is treated with a palladium catalyst and strong base; the B-aryl group undergoes a net migration to the C3 position (Scheme 35).…”