116酯缩合反应 Ester Condensation reactions
Organic Chemistry Organic Chemistry Xiamen Xiamen University University 11.6 酯缩合反应 Ester Condensation Reactions
The claisen condensation reaction Esters, like aldehydes and ketones,are weakly acidic. When an ester with an alpha hydrogen is treated with one equivalent of a base such as sodium ethoxide, a reversible condensation reaction occurs to yield a p-keto ester product. This reaction between two ester components is known as the Claisen condensation reaction
Organic Chemistry Organic Chemistry Xiamen Xiamen University University The Claisen Condensation Reaction Esters, like aldehydes and ketones, are weakly acidic. When an ester with an alpha hydrogen is treated with one equivalent of a base such as sodium ethoxide, a reversible condensation reaction occurs to yield a β−keto ester product. This reaction between two ester components is known as the Claisen condensation reaction
a For example, ethyl acetate yield ethyl 3 acetoacetate on treatment with base EtoNa H,O oO C:2 CH3COEt EtoH H + CH2C-CHcOEt EtOH ⑤.乙酸乙酯 乙酰乙酸乙酯 Ethyl acetate Ethyl acetoacetate g Claisen酯缩合:含α氢的酯在碱的作用下 两分子酯发生缩合反应,生成β-羰基酸酯同 时消去一分子醇
Organic Chemistry Organic Chemistry Xiamen Xiamen University University For example, ethyl acetate yield ethyl acetoacetate on treatment with base. CH 3COEt O 2 EtOH EtONa H 2 O H + CH 3 C O CHCOEt O + E t O H 乙酸乙酯 乙酰乙酸乙酯 E thyl acetate Ethyl acetoacetate Claisen 酯缩合 含α−氢的酯在碱的作用下 两分子酯发生缩合反应 生成 β−羰基酸酯同 时消去一分子醇
Mechanism CH3 CO2Et+ EtO-CH2CO2Et EtOH 3. pKa 24-5 CH3-C-OEt +)CH2CO2Et-CHx-C-OEt CH,CO Et 一—CH3-C-CH2CO2Et+EtO O EtO 9CH3-C-CH, CO,= -CH3-C-CHCO2Et+ EtOH pKa 11 CH3C-Ch, Co,Et
Organic Chemistry Organic Chemistry Xiamen Xiamen University University Mechanism CH 3CO 2Et + EtO − − CH 2CO 2Et + EtOH CH 3 C OE t O − + CH 2CO 2Et CH 3 C O E t O − CH 2CO 2Et CH 3 C CH 2CO 2Et O + EtO − CH 3 C CH 2CO 2Et O EtO − CH 3 C − CHCO 2Et O + EtOH H + CH 3 C C H 2CO 2Et O pKa 24.5 pKa 11
g只含一个-H的酯缩合时用更强的碱促使 平衡移动 E2(CH3)2CHCO2 C2H5 +(C6H3)CN3 ELO o cH ( CH3)2CH-C-CCO2C2H5 +( C6H5)3CH pKa 36 (C6H5)3C o cH C(CH3)2C-C-CCO2C2H5 CH
Organic Chemistry Organic Chemistry Xiamen Xiamen University University 只含一个α− H的酯缩合时用更强的碱促使 平衡移动 2 (CH 3 ) 2CHCO 2 C 2 H 5 + (C 6 H 5 ) 3 C − Na + Et 2 O + (C 6 H 5 ) (C H 3 ) 2CH C CCO 2 C 2 H 5 3 C H O CH 3 CH 3 (C H 3 ) 2 C C CCO 2 C 2 H 5 O CH 3 CH 3 (C 6 H 5 ) 3 C pKa 36