No abstract

Asymmetric AlPh(3) (THF) additions to a wide variety of aldehydes catalyzed by a titanium catalyst of 20 mol % 1,3-bis[N-sulfonyl-(1R,2S)-1,3-diphenyl-2-aminopropanol]benzene (1) are reported. The catalytic system works excellently for aromatic aldehydes bearing either an electron-donating or an electron-withdrawing substituent on the aromatic ring to afford secondary diaryl alcohols in excellent isolated yields of >or=95% and excellent enantioselectivities of >or=94% ee. The phenyl addition to cinnamaldehyde or 2-furylaldehyde gave corresponding secondary alcohols in 85% and 95% ee, respectively. For aliphatic aldehydes, increasing enantioselectivities of the addition products in terms of increasing steric sizes of aldehydes are observed, and this trend goes from the linear 1-pentanal (87% ee), the secondary cyclohexylaldehyde (95% ee) or the 2-methylpropanal (97% ee), to the tertiary 2,2-dimethylpropanal (99% ee).

Mediated 6-endo Cyclization. -A facile, mild, and selective method for the synthesis of benzopyran derivatives is reported. o-Alkynoylphenyl acetates obtained from either acyl chloride derivative (I) or substituted salicylates (VIII) by Sonogashira coupling with terminal alkynes (II) are subsequently converted into benzopyranones within a few minutes in the presence of 18-crown-6 ether. For the parafluorophenyl derivative (IIIf) defluorination of the desired product is observed by treatment with potassium methoxide. -(CHUANG, D.-W.; EL-SHAZLY, M.; BALAJI D., B.; CHUNG, Y.-M.; CHANG*, F.-R.; WU, Y.-C.; Eur. J. Org. Chem. 2012, 24, 4533-4540, http://dx.

<p>PDF file, 75KB.</p>

<p>PDF file, 984KB.</p>