1079366-52-1Relevant academic research and scientific papers
Ir-Catalyzed ortho-Borylation of Phenols Directed by Substrate-Ligand Electrostatic Interactions: A Combined Experimental/in Silico Strategy for Optimizing Weak Interactions
Chattopadhyay, Buddhadeb,Dannatt, Jonathan E.,Andujar-De Sanctis, Ivonne L.,Gore, Kristin A.,Maleczka, Robert E.,Singleton, Daniel A.,Smith, Milton R.
supporting information, p. 7864 - 7871 (2017/06/20)
A strategy for affecting ortho versus meta/para selectivity in Ir-catalyzed C-H borylations (CHBs) of phenols is described. From selectivity observations with ArylOBpin (pin = pinacolate), it is hypothesized that an electrostatic interaction between the partial negatively charged OBpin group and the partial positively charged bipyridine ligand of the catalyst favors ortho selectivity. Experimental and computational studies designed to test this hypothesis support it. From further computational work a second generation, in silico designed catalyst emerged, where replacing Bpin with Beg (eg = ethylene glycolate) was predicted to significantly improve ortho selectivity. Experimentally, reactions employing B2eg2 gave ortho selectivities > 99%. Adding triethylamine significantly improved conversions. This ligand-substrate electrostatic interaction provides a unique control element for selective C-H functionalization.
Regio- and stereoselective ring opening of enantiomerically enriched 2-aryl oxetanes and 2-aryl azetidines with aryl borates
Bertolini, Ferruccio,Crotti, Stefano,Di Bussolo, Valeria,Macchia, Franco,Pineschi, Mauro
supporting information; experimental part, p. 8998 - 9007 (2009/04/11)
(Chemical Equation Presented) The regioselective ring opening of 2-aryl-substituted four-membered heterocyclic rings with phenols, including catechol, was achieved by the use of aryl borates in mild and neutral reaction conditions without the aid of any transition metal catalysts. While β-alkyl azetidines were found not to be reactive, optically active N-tosyl azetidines gave the corresponding β-aryloxy amines in a racemic form, thus indicating the considerable carbocationic character of the transition state. The introduction of a hydroxyl group in the azetidine ring (i.e., an azetidinol), able to anchor the aryl borate and to direct the subsequent nucleophilic delivery, was shown to determine the ring-opening process with predominant inversion of configuration. When enantiomerically enriched 2-aryl oxetanes were used, the reduced extent of racemization observed (up to 93:7 er) was rationalized by an intramolecular delivery through a six-membered transition state, giving β-aryloxy alcohols with a predominant retention of configuration (i.e., a syn-stereoselective ring opening). The aryloxy alcohols obtained, endowed with suitable functionalities, can be cyclized to give access to enantiomerically enriched 2-aryl-1,5-benzodioxepins.
