《Sodium Tetraalkoxyborates Intermediates ...》.pdfVIP

FULL PAPER DOI: 10.1002/ejoc.200900352 Sodium Tetraalkoxyborates: Intermediates for the Quantitative Reduction of Aldehydes and Ketones to Alcohols through Ball Milling with NaBH4 M. Reza Naimi-Jamal,*[a] Javad Mokhtari,[a] Mohammad G. Dekamin,[a] and Gerd Kaupp*[b] Keywords: Alcohols / Sustainable chemistry / Carbonyl compounds / Hydrogen transfer / Borates Stoichiometric molecular solid-state vibrational ball milling, and stereoselective. Varied substituents are not attacked, in- solvent-free kneading ball milling, and mechanochemical cluding the bromine of α-bromo ketones. Conjugated alde- ball milling of varied aldehydes and ketones with unmodified hydes and ketones provide quantitative yields of the allylic sodium borohydride under temperature control uses all hy- alcohols free of contamination by saturated alcohols that drogen atoms of the reducing agent in fast reactions. It pro- would occur by reaction in solution. Depending on the stoi- vides quantitative yields of thermally stable sodium tetraalk- chiometric ratio, benzil is quantitatively reduced to benzoin oxyborates. The easily isolated solids are extremely sensitive (4:1 ratio) or dihydrobenzoin (2:1 ratio). towards hydrolysis, leading to quantitative yields of the cor- (© Wiley-VCH Verlag GmbH Co. KGaA, 69451 Weinheim, responding alcohols. The rapid syntheses are regiospecific Germany, 2009) Introduction been used to improve the situation. Furthermore, other re-