Dimenthyl succinate

The dilithium enolate of dimenthyl succinate (15) has been systematically studied in its reaction with 1,co-dihalides102. The trans/cis ratio is ca. 10 1-19 1, yields are in the region of >60% and the diastereoselectivitiy is unexpectedly high (see Table 6). 

Condensation of (-)-Dimenthyl Succinate Dianion with 1, u-Dihalides (-)-Dimenthyl Cyclopropane-(lS,2S)-1,2-dicarboxylate... 

The cooperative effect ( 1.6) of two esters can improve selectivity Alkylation of dimenthyl succinate 1.21 (n = 2) by BrCH Cl in the presence of base leads, after hydrolysis, to nonracemic trans- 1,2-cyclopropanedicarboxylic acid with an excellent enantiomeric excess [12] (Figure 5.17). However, on the way to estrone, Quinkert and coworkers had to use (l ,2ft5S)-phenmenthol dimalonale 5.26 to synthetize methyl 2-vinylcydopropane-l, l-dicaibcogdate with a good enantiomeric excess (Figure 5.17). 

Dimenthyl succinate Butanedioic acid, b1sL5-methy1-2- l-methy1ethyl)-cyclohexyl]ester, [lR-[la lR, 2S, 5R ),26,5a)]- (9) (34212-59-4)... 

Chiral 1,2-cycloalkanedicarboxylic acids.1 This ring system can be obtained by coupling 1,co-dihalides or -ditosylates with the dienolate of d- or /-menthyl succinate (1). The dienolate generated with lithium 2,2,6,6-tetramethylpiperidide is mainly the (E,E)-isomer, whereas deprotonation with LDA and HMPT generates mainly the (Z,Z)-isomer. Thus reaction of 1 (R = /-menthyl) with LiTMP in THF at -78° with CH2BrCl results in (S,S)-( - )-dimenthyl cyclopropane-frww-1,2-dicarboxylate (2) in 58% chemical yield and 99% de. A similar reaction of 1, R = d-menthyl, results in (R,R)-2 in 60% yield and 80% de. 

A. ( ) Dimenthyl euaeinate. A 300-mL, one-necked, round-bottomed flask is equipped with a magnetic stirrer, Dean-Stark trap, and a reflux condenser. The flask is charged with 20 g (0.2 mol) of succinic anhydride. 

Initially applied to thermal cydoaddition of fumarates of chiral alcohols with anthracene [118] (Figure I.34.a), cooperativity was extended to other reactions of symmetrical diesters. While reactions of mixed diesters bearing a single chiral alcohol residue are poorly stereoselective, those of symmetrical diesters can be quite useful. Indeed, the formation of cyclopropane diesters 43 from succinic add diesters and BrCB Cl is poorly diastereoselective when using a mixed methyl and menthyl ester. But it becomes highly diastereoselective when performed with symmetrical dimenthyl esters (Figure I.34.b). 

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