TiCl4/NaBH4 reduction of some functional groups

[demorol]

Reduction of Some Functional Groups with Titanium(IV) Chloride/Sodium Borohydride
Shinzo KANO, Yasuyuki TANAKA, Eiichi SUGINO, Satsoshi HIBINO

Synthesis 1980, 695
DOI:

10.1055/s-1980-29174

Reduction of Carboxylic Acids, Acyl Chlorides, Carboxamides, and Oximes; General Procedure:

Amounts of Reagent used for 10 mmol of substrate:

Carboxylic Acids: TiCl₄, 2.09g (11 mmol); NaBH₄, 1.25g (33 mmol).
Acyl Chlorides: TiCl₄, 2.09g (11 mmol); NaBH₄, 0.83g (22 mmol).
Carboxamides and Lactams: TiCl₄, 2.85g (15 mmol); NaBH₄, 1.13g (30 mmol).
Oximes: TiCl₄, 3.99g (21 mmol); NaBH₄, 1.59g (42 mmol).

Procedure: A solution of the substrate (10 mmol) in anhydrous 1,2-dimethoxyethane (10 mL) is added dropwise to an ice-cooled, stirred mixture of TiCl₄ and NaBH₄ in anhydrous 1,2-dimethoxyethane (40 mL). Stirring is continued for 14 h at room temperature and the reaction then quenched by the addition of water (100 mL) with ice cooling. In the case of carboxylic acids, the mixture is extracted with benzene (2 × 60 mL). In the other cases the mixture is basified with 28% aqueous ammonia and then extracted with benzene (2 × 70 mL). The extracts is washed with saturated NaCl solution (100 mL), dried with sodium sulfate, and evaporated. The products thus obtained are spectroscopically pure. They are furteh purified by distillation or recrystallization.