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

Table 4

Comparison of regioselective 1,2-reduction of 𝛼,𝛽-unsaturated carbonyl compounds with NaBH₄/Ba(OAc)₂ system and other reported systems.

Entry	Reducing systems	Molar ratio, ^atime (h), and yield (%)
		Cinnamaldehyde	Citral	Benzylideneacetone	Chalcone	β-ionone	2-cyclohexenone
1	NaBH4/Ba(OAc)2	(0.5)(0.08)(94)	(0.5)(0.08)(93)	(2)(0.25)(95)	(2)(0.25)(96)	(2)(0.25)(97)	(2)(0.25)(95)
2	Ph3PMeBH4	(1)(Im)(95)	—	(1)(3.5)(90)	(1.2)(6)(90)	(1)(6)(71)	—
3	NaBH3(OAc)	(1.67)(20)(70)	(1.67)(20)(70)	(1.67)(20)(86)	—	—	(1.67)(20)(32)
4	NaBH3CN	(2)(90)(80)	—	(2)(90)(77)	(3)(150)(0)	(2)(120)(88)	—
5	Li-n-BuBH3	—	—	(1)(2)(98)	(2)(2)(99)	(1)(2)(98)	(1)(2)(84)
6	(i-PrO)2TiBH4	(1)(0.08)(90)	(1)(0.08)(95)	—	—	—	—
7	NaBH4/C	(0.5)(Im)(92)	(0.5)(0.16)(92)	(2)(0.67)(96)	(2)(0.4)(98)	(2)(0.5)(91)	—
8	NaBH4/wet SiO2	(1)(0.016)(96)	(1)(0.066)(95)	(2)(0.15)(97)	(2)(0.25)(98)	(2)(0.25)(97)	—
9	NaBH4/Dowex1-8x	(1)(0.7)(96)	(1)(1.3)(94)	(1)(1.4)(98)	(1)(0.7)(95)	(1)(2.2)(91)	(1)(0.8)(89)
10	NaBH4/DOWEX(R)50WX4	(1)(0.25)(97)	(1)(0.33)(94)	(2)(0.91)(95)	(2)(1.5)(95)	—	—

 ^aReducing agent/substrate. Im: immediately.