Reduction of a,- unsaturated carbonyl compounds Edited by Chen Peng, Gao Dong
Reduction of a,b - unsaturated carbonyl compounds Edited by Chen Peng , Gao Dong
Part one Chemoselective Reductions or not?
Part one Chemoselective Reductions or not?[1]
By Nabh4 or LiAlH4 A is obtained orb ??? O OH HO C=c—C C=c—C +H—C—C—C H H B
By NaBH4 or LiAlH4 A is obtained or B ??? C C C O C C C O H H C C C HO H H H + A B
Substrate Yield.NaBHa, 50% aqueous EtoH- LiAlH, ether- %o A 7 B Yield, %o 7A %O B CH,-CHCCH( CHCH=CHOCH,(2) 65 35 98 (CHA)C=CHOCH(3) 92 59 97 100 CH, "CHCH (6) CHCHe CHCH (7) 92 94 100 CH=C-cH⑧ ≥99 ≤1 98 ≥99 ≤1 CHO
Other way to illustrate CH3 O (CH3)2C-CHCCH3 2HC-C-CH2 CHCH2 OH OH C OH (CH3)2C-CHCHCH2 (CH3)2CHCHCHCH2 H2C=CCH2 CHCH2 22 23 Starting - meteria 一 Product distribution %6 3 21 Reduction conditions %o12 22 %23 97 3 LiAlH, ether 60 40 LiAIH, ether 040 97 3 NaBH4, 50%o aq ethanol 97 3 NaBH, 507 aq methanol 87 10 3 60 40 NABH, i-PrOH 561725 97 3 NaBH, i-PrOH 542817
H2C C CH3 CH2CHCH2 OH CHCH2 OH (CH3)2C CH CHCH2 OH (CH3)2CHCH2 + + CHCCH3 O (CH3)2C 2HC C CH3 CH2CHCH2 O + 3 21 12 22 23 Other way to illustrate
attention the effect NaBH4 of solution!! I-ProH H A B
attention the effect of solution!! O NaBH4 i-PrOH O C + O H O B + H H H H O A H H
TABLE II REDUCTION BY SODIUM BOROHYDRIDE IN ISOPROPYL ALCOHOL Produet distribution Substr我te Yield,%% A %o B 7 C 10 60 34 83 65 34 25 48 63 37 0 69 53 26 21 26 8 ≥95 ≤4 Substrates 1to 9 refer to page 4
Substrates1to 9 refer to page 4
Summery: NaBH4 reduction with i-PrOH fast i-PrOh c=c-c—OBoR)4 c=c-c—0H+B(oi-Pr)4 BH H OH BH i-PrOh C=C-C c一c=c-0B(OR)4 c-c—c 19 i-PrOE i-PrO C-C-C BH4,c一
Summery:NaBH4 reduction with i-PrOH C C C O C C C OB(OR)4 - H C C C OH H + B - (Oi -Pr)4 fast i -PrOH BH4 - C C C OB(OR)4 - H C C C O 19 19 C C C OH i -PrOH + BH4 - H C C C O O C C C OH O H + 19 BH4 - 20 i -PrOH i -PrO - BH4 -
Summery of part one Both nabh4 and lialh4 have been observed to give both types of product, although the extent of reduction to saturated alcohol is usually greater with NaBH4 Solution can lead to other product See part two to further research
Summery of part one • Both NaBH4 and LiAlH4 have been observed to give both types of product , although the extent of reduction to saturated alcohol is usually greater with NaBH4 • Solution can lead to other product See part two to further research
Part two Several reagents have been developed which lead to exclusive 1.2- or 1 4-reduction
Part two Several reagents have been developed which lead to exclusive 1,2- or 1,4-reduction