Reductions of aryl bromides in water at room temperature

Abstract

Micellar nanoreactors derived from commercially available ‘Nok’ (SPGS-550-M), in the presence of Fu’s catalyst and a mild hydride source (NaBH4), are useful for facile debromination of functionalized aromatic derivatives. This mild and environemntally responsible process is utlized in water at room temperature, and the reaction mixtures can be smoothly recycled.

Catalytic Organic Reactions in Water toward Sustainable Society

“…In some examples, such as palladium-mediated reductions of aryl bromides, the use of Nok enabled the highest levels of conversion. 620 Similarly, Tan very recently discovered that the sequential regioselective C−H functionalization of thiophenes could be achieved in water in the presence of Nok as the surfactant (Scheme 142). 621 Interestingly, water was identified as the optimal solvent that could limit the decomposition of the substrates and products.…”

“…Nok employed β-sitosterol as the interior component, and was, therefore, much less expensive than the second-generation amphiphile TPGS-750-M, which was based on expensive vitamin E. In many cases, Nok exhibited reactivities similar to those achieved by TPGS-750-M. In some examples, such as palladium-mediated reductions of aryl bromides, the use of Nok enabled the highest levels of conversion . Similarly, Tan very recently discovered that the sequential regioselective C–H functionalization of thiophenes could be achieved in water in the presence of Nok as the surfactant (Scheme ).…”

The Hydrophobic Effect Applied to Organic Synthesis: Recent Synthetic Chemistry “in Water”

“…Another common application is decontamination of polyhalogenated compounds which are viewed as environmental pollutants. Hence, a method for reduction of aryl bromides was developed in 2 wt % of the β‐sitosterol‐based surfactant Nok in the presence of 3 mol % of Pd[P( t Bu) 3 ] 2 , 0.5 equiv of NaBH 4 , and 1.5 equivalents of triethylamine (Scheme ) . The presence of salts in the aqueous medium impacts the size of the micelles, affecting the outcome of the reaction (from 61 % yield without NaCl to >99 % yield at [3 m ]).…”

“…Hence, am ethod for reduction of aryl bromides was developed in 2wt% of the b-sitosterol-based surfactant Nok in the presence of 3mol %o fP d[P(tBu) 3 ] 2 ,0 .5 equiv of NaBH 4 , and 1.5 equivalents of triethylamine (Scheme 22). [42] The presence of salts in the aqueousm edium impacts the size of the micelles, [43] affecting the outcome of the reaction( from 61 % yield withoutN aCl to > 99 %y ield at [3 m]). Thism ethod led to excellenty ields on numerous functionalized substrates, including aryl chloride, benzyl alcohol, and ketone or aldehyde (< 5% of the correspondinga lcohols were detected).…”

Discovery-Based SNAr Experiment in Water Using Micellar Catalysis

“…The dissolution of substrates into the micelles and, by extension, the high local concentrations of reactive partners within them allows the reactions to occur under mild conditions . Lipshutz designer surfactants have been applied to a variety of cross-coupling, substitution, reduction, and peptide coupling reactions. − Additionally, TPGS-750-M has been demonstrated to be suitable for use in an undergraduate organic chemistry laboratory for performing click chemistry and olefin metathesis . A key aspect of these methodologies is that their utilization results in significant cost and waste savings relative to the use of their traditional solvent counterparts …”