Identification of a Boron-Containing Intermediate in the Boron Tribromide Mediated Aryl Propargyl Ether Cleavage Reaction

Abstract

An alternate reaction mechanism for the boron tribromide mediated deprotection of aryl propargyl ethers based on the isolation of a key boron-containing byproduct is proposed. On the basis of the new mechanistic insight, we discovered that HBBr(2) x SMe(2) can also be used for cleaving aryl propargyl ethers.

Importance of the Support Properties for Immobilization or Purification of Enzymes

“…First, we adapted the established bromoboration conditions to our needs (Scheme ). When using simple model alkynes such as 1‐heptyne ( 8a ; Scheme , entry 1) or phenylacetylene ( 8b ; Scheme , entry 2), we found that it was most convenient to follow the procedure described by Yao et al to generate the corresponding boronic acids (i.e., 9 ) 13. These intermediates were not isolated, and instead, condensation with diol 1 14 was carried out directly to give the corresponding boronates (i.e., 10 ).…”

Fundamental and Applied Properties of Borocations

“…Haloboration of alkynes using trihaloboranes is well documented but is restricted to terminal alkynes due to limited electrophilicity at boron [83][84][85]. Calculations on haloboration indicated that increasing electrophilicity at boron results in haloboration becoming more exothermic, and the key transition state barrier also becomes lower in + (26 and 27, Fig.…”

Divergent Elementoboration: 1,3‐Haloboration versus 1,1‐Carboboration of Propargyl Esters

“…Conducting the reaction between PhBCl 2 and 1 a in a variation of solvents ([D 6 ]benzene, [D 8 ]toluene, CH 2 Cl 2 , C 6 H 5 Cl) appeared to make no difference in reactivity with all showing almost quantitative conversion within 9 hours. Additionally, trialling other boron reagents such as BCl 3 as well as the borocation [PhClB(2‐DMAP)][AlCl 4 ] were unsuccessful with a mixture of products prevailing as observed in the resultant multinuclear NMR spectra.…”