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Aminoindanol-derived ester

Gosh independently reported another anti-selective aldol addition process employing aminoindanol-derived esters 114 (Equation 11) [72]. These were subjected to enolization with excess TiCl, and Hiinig s base to furnish titanium 2-enolates, as determined by NMR spectroscopy. Addition reactions with a variety of aliphatic and unsaturated aldehydes, precomplexed with TiCl4, furnished the anti aldol adducts such as 116 in 44—97% yields and up to 99 1 anti/syn ratios of diastereomers. The stereochemical outcomes of the reactions have been attributed to chelated Zimmerman-Traxler transition state structures, such as 115. It is interesting to note that benzaldehyde, as the only aromatic aldehyde examined, yielded a 1 1.1 mixture of antijsyn products. [Pg.114]

Carbenes belong to the most investigated reactive species in the field of organic chemistry. Besides their role as excellent ligands in metal-based catalytic reactions, organic carbene catalysis has emerged as an exceptionally fruitful research area. In 2002, Rovis reported a highly enantioselective intramolecular Stetter reaction of unsaturated esters 50 derived from salicylaldehyde by the catalysis of chiral aminoindanol-derived triazolium salt 49 (Scheme 36.14) [20a]. [Pg.1077]

Ghosh also took advantage of the C—2 hydroxyl moiety of aminoindanols as a handle in the aldol reaction. Chiral sulfonamide 41 was O-acylated to give ester 42. The titanium enolate of ester 42 was formed as a single isomer and added to a solution of aldehyde, precomplexed with titanium tetrachloride, to yield the anft -aldol product 43 in excellent diastereoselectivities.63 One additional advantage of the ester-derived chiral auxiliaries was their ease of removal under mild conditions. Thus, hydrolysis of 43 afforded a ft -a-methyl- 3-hydroxy acid 44 as a pure enantiomer and cis-1-/ -1 o I y I s u I f on a m i do- 2 - i n da n ol was recovered without loss of optical purity (Scheme 24.7).63... [Pg.467]


See other pages where Aminoindanol-derived ester is mentioned: [Pg.330]    [Pg.331]    [Pg.110]    [Pg.112]    [Pg.1308]    [Pg.87]    [Pg.90]   
See also in sourсe #XX -- [ Pg.114 ]




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