Reductive deoxygenation of aryl aldehydes and ketones and benzylic, allylic, and tertiary alcohols by zinc iodide-sodium cyanoborohydride

Abstract

Sodium cyanoborohydride in the presence of zinc iodide is found to exhibit unique and selective reducing properties. The reagents reduce aryl aldehydes and ketones as well as benzylic, allylic, and tertiary alcohols to the corresponding hydrocarbons.

Reduction of Carbonyl to Methylene: Organosilane-Ga(OTf)3 as an Efficient Reductant System

“…Direct catalytic procedures are also reported but drastic reaction conditions are required (150-180 bar, 270-300°C) [23]. On the other hand, the reduction of aryl aldehydes and ketones have been successfully performed using metal hydride reagents such as aluminum hydride [24][25][26][27][28][29], boron hydride [30][31][32][33][34][35][36], or hydrosilane [37][38][39][40][41] with a combination of stoichiometric or excess amounts of Lewis or Brønsted acids. However, only few examples are available for reactions employing catalytic amount of Lewis or Brønsted acids [42].…”

Hydrodeoxygenation of benzophenone on Pd catalysts

“…In addition, classical reduction agents like Li/NH 3 [4], metal hydrides of lithium, natrium, silicium or selenium (e.g. LiAlH 4 [5], NaBH 4 -Al 2 Cl 3 [6], NaBH 3 CN-TMSC [7], ZnI 2 -Na CNBH 4 [8], NaAlH 2 (OCH 2 CH 2 CH 3 ) 2 [9], Et 3 SiH in CF 3 COOH [10], Ph 2 SiH [11], PhSeH [12], Se with carbon monoxide and water [13]) or Cp 2 Ti(CO) 2 [14]) are used for these transformations. Last but not least, hydrogenation or hydrogenolytic reactions are used to transform benzophenone.…”

Mildly and highly selective reductive deoxygenation of para‐di‐ and monoalkylaminophenyl ketones by borane

“…Reductive deoxygenation of aryl ketones is an important and valuable procedure in organic synthesis [1][2][3][4]. There is a great need to develop novel methodologies for defunctionalization, especially for conversion of polyfunctional natural products to useful building blocks and bioactive molecules.…”

“…Although classical Clemmensen and Wolff-Kishner reduction use rather harsh acidic or basic conditions that are incompatible with the high degree of selectivity required for polyfunctional compounds, a number of milder direct and indirect methods have been proposed. The direct methods include (1) sodium (cyano)borohydride in the presence of some Lewis acids, such as boron trifluoride etherate [5,6], aluminum chloride [7], palladium chloride [8], zinc halide [2], or protic acid such as trifluoroacetic acid [9]; (2) borane in the presence of some Lewis acids [3], such as boron trifluoride etherate, aluminum chloride, zinc halide, titanium chloride, iron chloride, etc. or protic acid trifluoroacetic acid [10]; (3) lithium aluminum hydride in combination with aluminum chloride [11]; (4) trialkyl silane and acids; (5) hydrosiloxane-borane combination [4].…”