Crotonic acid methyl ester

Methyl-2-cyclohexen-l-one 2-Cyclohexen-l-one, 3-methyl- (8,9) (1193-18-6) (E)-Methyl crotonate Crotonic acid, methyl ester, (E)- (8) 2-Butenoic acid, methyl ester, (E)- (9) (623-43-8)... 

Fig. 1.31. The Wohl-Ziegler bromination of crotonic acid methyl ester D exclusively supplies the bromocrotonic ester G. However, vinyl acetic acid ester C and NBS exclusively yield the dibromo addition product B under Wohl-Ziegler conditions. Here, NBS acts as a Br2 source for addition rather than substitution. The fact that vinyl acetic acid ester and NBS do not react likewise to yield the bromocrotonic ester G is due to an electronic effect discussed in the text.

With fram-crotonic acid methyl ester, dimethylsulfoxonium methylide forms a cyclopropane stereoselectively (Figure 9.3, bottom). Therein, the methyl group and the COzMe group retain the trans orientation they had in the crotonic ester. Thus, the fnms-crotonic ester is cyclopropanated with complete retention of the configuration. 

Fig. 9.3. The pair of reactions illustrates the occurrence of stereoselectivity and the lack of stereospecificity in two cyclopropanations with an S ylide. The trans-crotonic acid methyl ester reacts with complete retention of the configuration, whereas the di-crotonic acid methyl ester reacts with complete inversion.

CAS 623-43-8 EINECS/ELINCS 210-793-7 Synonyms 2-Butenoic acid, methyl ester, (E)- trans-2-Butenoic acid methyl ester Crotonic acid, methyl ester, (E)- (E)-Crotonic acid methyl ester Methyl (2E)-2-butenoate Methyl trans-2-butenoate Methyl o-crotonate Methyl E-crotonate Methyl trans-crotonate trans-Methyl crotonate Empirical C5H8O2 Formula CH3CH=CHC(0)0CH3 Properties Colorless liq. m.w. 100.1 sp.gr. 0.945 b.p. 116-120 C flash pt. (CC) -1 C ref. index 1.425... 

C5H7CIO2 2-chloro-tra s-crotonic acid methyl ester 22038-57-9... 

C5 H7 Cl 02 3-chloro-trans-crotonic acid methyl ester 6214-25-1... 

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