Regioselective and Chemoselective Reduction of 𝜶,𝜷-Unsaturated Carbonyl Compounds by NaBH₄/Ba(OAc)₂ as a Reducing System

Table 1

Optimization of reduction reaction of cinnamaldehyde to 3-phenyl-2-propen-1-ol and benzylideneacetone to 4-phenyl-3-buten-2-ol with NaBH₄/Ba(OAc)₂ as a reducing system.

Entry	Substrate	Molar ratio^a	Solvent	Time (min)	Conversion^b (%)
1	Cinnamaldehyde	1 : 0.5 : 0.5	CH3CN	2	100
2	Cinnamaldehyde	1 : 0.5 : 0.2	CH3CN	5	100
3	Cinnamaldehyde	1 : 0.25 : 0.5	CH3CN	60	>100
4	Cinnamaldehyde	1 : 0.5 : 0.2	THF	10	100
5	Cinnamaldehyde	1 : 0.5 : 0.1	CH3CN	10	100
6	Benzylideneacetone	1 : 1 : 0.5	THF	60	>100
7	Benzylideneacetone	1 : 1 : 0.5	CH3CN	60	>100
8	Benzylideneacetone	1 : 2 : 0.5	CH3CN	60	>100
9^c	Benzylideneacetone	1 : 2 : 0.5	CH3CN	15	100
10^c	Benzylideneacetone	1 : 2 : 0.2	CH3CN	20	100

 ^aMolar ratio as substrate: NaBH₄ : Ba(OAc)₂; ^bcompletion of the reactions was monitored by TLC (eluent; n-hexane/EtOAc: 9/1). ^cReaction was carried out under reflux conditions.