Acetals synthesis, asym

Amino(aryl)acetic acid esters -, synthesis, asym. 43, 794 44, 678 2-Amino-1 -arylalcohols... 

Asym. synthesis. A stirred soln. of startg. optically pure dioxane (prepared from (S)-( + )-butane-l,3-diol) and 4 eqs. of ethyl bromozinc-acetate (prepared from ethyl bromoacetate and Zn-Cu couple) in methylene chloride at —78° treated with 3 eqs. TiCl4, and quenched with 10% NaHC03 when reaction complete ca. 1 h) - product. Y 82% (diastereomer ratio 3.0 1). F.e. with racemic acetals s. T. Basile et al., J. Chem. Soc. Chem. Commun. 1989, 596-7 chiral a-alkoxynitriles with Me3SiCN/TiCl4 s. A. Solladie-Cavallo et al.. Tetrahedron Letters 29, 2955-8 (1988). 

Asym. synthesis of alkoxy-2-acetylenes from cyclic acetals G... 

Asym. synthesis. A soln. of penta-O-acetyl-D-galactose diethyl dithioacetal and mercuric acetate in acetic anhydride-acetic acid (1 1) heated on a water bath until the temp, of the mixture has reached 80° a-l,2,3,4,5,6-hexa-0-acetyl-D-galactose S-ethyl monothioacetal, a single diastereomer. Y 1S%, F. e. s. E. P. Painter, Can. J. Chem. 42, 2018 (1964). 

Dilithium tetrachlorocuprate is recommended as an additive for cross coupling of Grignard compounds with tosylates even allylic and benzylic acetates give good yields . a-Methylene-ketones, -carboxylic acids and -lactones have been prepared via sulfides and sulfoxides. A convenient and general synthesis of acetylene derivatives from boranes via the reaction of iodine with lithium 1-alkynyltriorganoborates has been published ar-Nitrostyrenes can be easily obtained by a Wittig synthesis with formaldehyde in an aqueous medium . A new synthesis of unsym. ketones by reaction of dialkyldiloroboranes with lithium aldimines has recently been published . Metallo aldimines have also served for the synthesis of a variety of other compound classes such as a-hydroxyketones, a-keto acids, nitriles, and for the asym. synthesis of a-amino acids . Polycondensations of malononitriles with benzylic chlorides have been carried out quantitatively under mild conditions in dimethyl sulfoxide with triethylamine as acid acceptor . Carbonyl compounds can react with dibromoacetonitrile to yield a-bromo esters with additional carbon atom . ... 

A remarkable ring closure of polyenic acetals can be performed in a highly stereospecific manner with SnCl4 to form polycyclic products with a multiplicity of asym. centers. 3-Alkyl-4-halogeno-tetrahydropyrans can be obtained by a novel reaction of olefins with paraformaldehyde and hydrogen halides . 1,3-Diphenyl-naphtho[2,3-c]furan, the first known stable 2,3-naphthoquinonoid, is an extremely reactive diene component in Diels-Alder syntheses . A modified Pechmann coumarin synthesis uses enamine derivatives of yS-ketoacids without catalyst. ... 

Yokomatsu T, Shibuya S (1992) Enantioselective synthesis of a-amino phosphonic acids by an application of stereoselective opening of homochiral dioxane acetals with triethyl phosphite. Tetrahedron Asym 3 377-378... 

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