Lewis Acidity in Haloalkyl Orthoborate and Metaborate Esters

Direct Synthesis of Amides from Carboxylic Acids and Amines Using B(OCH2CF3)3

“…Commercially available trimethoxyboroxine 1 is reported to be a stronger Lewis acid than both B(OMe) 3 and B(OCH 2 CF 3 ) 3 but did not offer any significant advantage in the amidation reaction (entry 7). 14 Interestingly, the reaction with 1 did not lead to comparable conversions even after a 15 h reaction time (entry 8). This may be due to the fact that 1 can more readily form oligomeric species such as B 2 O 3 upon heating, and such species are much less active in the amidation reaction.…”

“…We therefore sought an alternative method for preparing the amidation reagent. The synthesis of B(OCH 2 CF 3 ) 3 has been previously reported from boric acid 14 and from B 2 O 3 . 15 We found the latter procedure to be particularly straightforward on multigram scale.…”

Supramolecular structures containing ‘isolated’ pentaborate anions and non-metal cations: Crystal structures of [Me3NCH2CH2OH][B5O6(OH)4] and [4-MepyH, 4-Mepy][B5O6(OH)4]

“…B(OCH 2 CF 3 ) 3 was prepared by a published procedure [15,16]. 11 B and 13 C NMR spectra were recorded on a Bruker 500 AVANCE spectrometer operating at 160 and 125 MHz, respectively.…”

“…1 Compound 2 was obtained in a low yield from a prolonged attempt of a re-crystallization of the orthoborate ester adduct (4-Mepy) AE B(OCH 2 CF 3 ) 3 [15]. It is believed that hydrolysis occurred by adventitious H 2 O in the solvent, and that the hydrolysis was facilitated by the enhanced Lewis acidity of the tris(trifluoroethoxy)orthoborate moiety [16]. There is precedent for such a reaction since pre-meditated hydrolysis of the orthoborate ester B(OMe) 3 in the presence of organic bases (e.g.…”

Borate-assisted liquid-phase selective oxidation of n-pentane

“…These observations agree with the findings of Itskovich et al [22], McMahon and Chafetz [56] and Illingworth [57], who investigated the oxidation of alkanes and cycloalkanes with various types of boron compounds, and reported that alkyl metaborates give better selectivity and less inhibition of the oxidation than trialkyl orthoborates and boric acid. The fact that s-BuMB gives better selectivity than the same concentrations of TiPrB and boric oxide can be explained by the higher Lewis acidity of alkyl metaborates compared to alkyl orthoborates and boric oxide [52,58,59].…”