88371-29-3Relevant academic research and scientific papers
Enantioselective [4+2]-Cycloaddition Reaction of a Photochemically Generated o-Quinodimethane: Mechanistic Details, Association Studies, and Pressure Effects
Grosch, Benjamin,Orlebar, Caroline N.,Herdtweck, Eberhardt,Kaneda, Masayuki,Wada, Takehiko,Inoue, Yoshihisa,Bach, Thorsten
, p. 2179 - 2189 (2007/10/03)
1,2,3,4-Tetrahydro-2-oxoquinoline-5-aldehyde (2) was prepared from m-aminobenzoic acid and 3-ethoxyacryloyl chloride (4) in 19% overall yield. Compound 2 underwent a photochemically induced [4+2]-cyclo-addition reaction with various dienophiles upon irradiation in toluene solution. The exo product 10 a was obtained with acrylonitrile (9a) as the dienophile, whereas methyl acrylate (9b) and dimethyl fumarate (9c) furnished the endo products 11b and 11c (69-77% yield). The reactions proceeded at -60°C in the presence of the chiral complexing agent 1 (1.2 equiv) with excellent enantioselectivity (91-94% ee). The enantiomeric excess increases in the course of the photocycloaddition as a result of the lower product association to 1. The intermediate (E)-dienol 8 was spectroscopically detected at -196°C in an EPA (diethyl ether/isopentane/ethanol) glass matrix. The association of the substrate 2 to the complexing agent 1 was studied by circular dichroism (CD) titration. The measured association constant (KA) was 589 M-1 at room temperature (25°C) and normal pressure (0.1 MPa). An increase in pressure led to an increased association. At 400 MPa the measured value of KA was 703 M-1. Despite the stronger association the enantioselectivity of the reaction decreased with increasing pressure. At 25°C the enantiomeric excess for the enantioselective reaction 2 + 9a→10a decreased from 68% ee at 0.1 MPa to 58% ee at 350 MPa. This surprising behavior is explained by different activation volumes for the diastereomeric transition states leading to 10a and ent-10a.
Carbostyril derivatives
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, (2008/06/13)
Disclosed are carbostyril derivatives and their salts of the formulas STR1 The compounds have anti-peptic ulcer effects, and are useful as a treating agent for curing peptic ulcers in the digestive system, such as ulcers in the stomach and in the duodenum. The compounds particularly have prophylaxis and curing effects for treating chronic ulcers, for example experimental acetic acid-induced ulcers and cautery ulcers, with both low toxicity and few side-effects. Also disclosed are processes for preparing the compounds and for preparing pharmaceutical compositions containing them.
