Carboxylic acid derivatives synthesis variations

The other significant variation of the prototypical Kulinkovich reaction is the so-called Kulinkovich-de Meijere reaction, where de Meijere extended the substrates from esters to amides. Other carboxylic acid derivatives including (cyclic) carbonate, imides, and nitriles also react with the key Kulinkovich intermediate. Szymoniak developed an efficient new synthesis of cyclopropanes via hydrozirconation of allylic ethers (e.g., using Cp2Zr(H)Cl) followed by addition of a Lewis acid (e.g., BFa OEta). Casey et al. further investigated the stereochemistry of this interesting cyclopropanation reaction using deuterated allylic ethers. ... 

Once bearing some substituents, the decrease of polarity of the sucrose derivatives makes them soluble in less-polar solvents, such as acetone or tert-butanol, in which some lipases are able to catalyze esterifications. Unlike proteases, which necessitate most often the use of an activated acyl donor (such as vinyl or trifluoroethyl esters), lipases are active with simple esters and even the parent carboxylic acids in the presence of a water scavenger. The selectivity of the lipase-catalyzed second esterification is specific for OH-6 allowing the synthesis of mixed T,6 -diesters.123,124 For some lipases, a chain-length dependence on the regiochemistry was observed.125 Selectively substituted monoesters were thus prepared and studied for their solution and thermotropic behavior.126,127 Combinations of enzyme-mediated and purely chemical esterifications led to a series of specifically substituted sucrose fatty acid diesters with variations in the chain length, the level of saturation, and the position on the sugar backbone. This allowed the impact of structural variations on thermotropic properties to be demonstrated (compare Section III.l).128... 

Variations in the 5-substituent of chiral oxazolines cause considerable fluctuations in the degree of asymmetrical alkylation of these substrates, showing that steric as well as chelation factors are important in this method of obtaining chiral carboxylic acids. An impressive example of asymmetric induction is the synthesis of 3-substituted-3-phenylpropionic acids (5) of ca. 99% optical purity, from the 1,4-oxazepine (4) (derived from a-ethoxycarbonylcinnamic acid and /-ephedrine hydrochloride), by Michael addition of Grignard reagents in the presence of nickel chloride, followed by hydrolysis and decarboxylation."... 

A variation on a literature procedure draws attention to a useful method for the synthesis of tetrolic acid. Copper dienolates derived from a,jS-unsatur-ated acids undergo y-alkylation with a regioselectivity of 91%. A full paper has appeared from Mulzer and his co workers on the control of 1,2-/1,4-regioselectivity in the additions of carboxylic acid dianions to a,jS-unsaturated carbonyl compounds. The addition of phenyl acetate dianion (23) (Scheme 20) to a,/3-un aturated aldehydes leads to the f/ireo-unsaturated /S-hydroxy-carboxylic acid (24) the threo and erythro ratio of 5 examples was >9 1. 

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