Aryl Trihydroxyborates:  Easily Isolated Discrete Species Convenient for Direct Application in Coupling Reactions

Abstract

A conceptually and practically simple alternative approach to the use of arylboron species as the organometallic component in cross-coupling processes is described whereby trihydroxyborate salts are isolated and directly employed. The protocol derives practical benefit from the ease and convenience of the isolation and subsequent use of the discrete borate salts, eliminates the need for additional base, and aids the use of correct reaction stoichiometry.

Pd-catalyzed Suzuki cross-Coupling reaction of bromostilbene: insights on the nature of the boron Species

“…[12][13][14] The fact that trihydroxyarylborates can be applied for the base-free Suzuki reaction with aryl halides is a strong experimental evidence. 8 Our results for the different boron species in the presence and absence of base (see Table 1) also goes in the same direction and our next step was to identify the boron species present during the coupling reaction. Electrospray ionization mass spectrometry (ESI-MS) is a powerful tool in the identification of organometallic reaction intermediates and has been applied to the detection of intermediates in palladium-catalyzed cross coupling reactions.…”

“…Potassium organotrifluoroborates have been used as an alternative to boronic acids and boronate esters, 7 and, more recently, aryl trihydroxyborate salts were isolated and employed in a base-free Suzuki cross-coupling reaction with aryl halides. 8 In order to investigate the role of the base we also used sodium trihydroxyphenylborate for the coupling with (E)-bromostilbene and in this case the coupling reaction occurs even in the absence of a base ( Table 1, entry 6).…”

“…(E)-bromostilbene, 5 arylboronic acids, 24 pinacol phenylboronate ester and sodium trihydroxyphenylborate 8 were prepared according to the previously published procedure. Other chemical were purchased from commercial sources.…”

Coordination Networks Based on Boronate and Benzoxaborolate Ligands

“…Their conjugate bases are the boronate (also called tri-hydroxyborate) and benzoxaborolate anions, in which the boron is in a tetrahedral environment (Figure 2). The tetrahedral nature of the boronate anion was elucidated in 1959 [16], but it is only in 2006 that a crystal structure involving such a boronate anion was described for the first time [17].…”

Síntese de aminoácidos não-proteinogênicos enriquecidos em 10B utilizados na Terapia de Captura de Nêutrons por Boro (BNCT)

“…Dentre os artigos selecionados (MIYAURA et al, 1995;MALAN;MORIN, 1998;YAMAMOTO et al, 2000;ASHTON et al, 2001;WOLAN, 2002;CAMMIDGE et al, 2006;YAMAKAWA et al, 2011;O'CONNELL et al, 2012;CHATANI et al, 2012), pode-se verificar a existência de três métodos em comum para essa substituição, sendo a fonte de boro utilizada nestes casos como sendo o B(OiPr) 3 (triisopropil borato) ou o pinacolborano (Figura 6). A não incorporação do átomo de magnésio no esqueleto carbônico da molécula pode ter sido fundamental para o insucesso desta etapa.…”