Several commercial Lewis acids, including those of the Bronsted type, specifically HBF(4).OEt(2), are able to catalyze the reaction between aromatic aldehydes and ethyl diazoacetate to produce 3-hydroxy-2-arylacrylic acid ethyl esters and 3-oxo-3-arylpropanoic acid ethyl esters. Reactions catalyzed by the iron Lewis acid [(eta(5)-C(5)H(5))Fe(+)(CO)(2)(THF)]BF(4)(-) (i.e., 1) have the best yields and greatest ratio of 3-hydroxy-2-arylacrylic acid ethyl ester. The product distribution of 1 is not affected in the presence of Proton Sponge, but is dependent on temperature and the nature of the substrate aldehyde, whereas the activity of HBF(4).OEt(2) is affected by the presence of Proton Sponge and is reactive at temperatures as low as -78 degrees C. Consequently, both 1 and HBF(4).OEt(2) are valuable catalysts in producing important 3-hydroxy-2-arylacrylic acid ethyl esters as precursors to biologically active compounds.

We have developed a convenient two-step procedure for the synthesis of 3-ethoxycarbonyl indoles from commercially available materials. The two-step procedure involves the synthesis of 2-aryl-3-hydroxypropenoic acid ester, followed by a catalytic reduction. This method is efficient, simple, and selective.

Indole derivatives R 0140 Convenient Method of Synthesizing 3-Ethoxycarbonyl Indoles. -(ISLAM, M. S.; BRENNAN, C.; WANG, Q.; HOSSAIN*, M. M.; J. Org. Chem. 71 (2006) 12, 4675-4677; Dep. Chem. Biochem., Univ. Wis., Milwaukee, WI 53201, USA; Eng.) -Jannicke 44-123

High yields of the biologically important 3-hydroxy-2-arylacrylates can be obtained under the optimized conditions shown. Starting from o-substituted aldehydes (V) cyclized products are formed. Acetophenone can also be converted with success in contrast to its fluoro analogue. -(DUDLEY, M. E.; MORSHED, M. M.; BRENNAN, C. L.; ISLAM, M. S.; AHMAD, M. S.; ATUU, M.-R.; BRANSTETTER, B.; HOSSAIN*, M. M.; J. Org. Chem. 69 (2004) 22, 7599-7608; Dep. Chem., Univ. Wis., Milwaukee, WI 53201, USA; Eng.) -Jannicke 11-099

Four Michael 1:1 adducts 2-[1,5-bis-(2-methoxyphenyl)-3-oxo-pent-4-enyl]-cyclohexane-1,3- dione 3a, 2-[1,5-bis-(2-methylphenyl)-3-oxo-pent-4-enyl]-cyclohexane-1,3-dione 3b, 2-[1,5-bis- (2-chlorophenyl)-3-oxo-pent-4-enyl]-cyclohexane-1, 3-dione 3c and 2-[1,5-Bis-(2-chloro- phenyl)- 3-oxo-pent-4-enyl]-5,5-dimethyl-cyclohexane-1,3-dione 3d have been synthesised by the application of Michael reaction between 1, 3-cyclohexanedione 1a or dimedone (5, 5-dimethylcy clohexane-1, 3-dione) 1b and trans,trans diarylideneacetone [1,5-diaryl-1,4-pentadien-3-one] 2a-c using acid catalyst. These adducts may be regarded as the intermediate of spiro [5.5] undecane compounds which can be achieved effectively via intramolecular cyclization of the Michael 1:1 adduct. The structures of the Michael 1:1 adducts 3a-d were determined by their UV, IR, 1H-NMR, 13C-NMR, DEPT-135 spectral data, HRMS and elemental analyses. Bangladesh J. Sci. Ind. Res.55(4), 283-288, 2020