Research In Synthetic Methodologies Of Cyclopentenone Esters And α,β-Unsaturated Esters

Cyclopentenone derivatives and α,β-unsaturated esters are two sorts of extraordinary important compounds. New methods for the syntheses of cyclopentenone esters and a, p-unsaturated esters were investigated in this paper. The paper is divided into three parts. The main results are summarized as follows.1.2-Cyclopenten-l-one-5-carboxylic ester derivatives were synthesized via Rh₂(OAc)4-mediated intramolecular C-H insertion reaction of the corresponding 4Z-P-vinyl-P-oxo-a-diazo esters, which were synthesized in three-step or four-step sequence starting from alkynic aldehydes. These intramolecular C-H insertion reactions were performed in excellent chemical selectivity to only afford intramolecular C-H insertion products without any Wolff rearrangement products. The substitution group on S-position of p-vinyl-p-oxo-α-diazo esters played an important role in the formation of product. When substituent is an alkyl group, the decomposition of the diazo compounds afforded cyclopenten-1-one-5-ca-rboxylic ester derivatives. When substituent is an aryl group, 2-hydroxynaphthoate was an exclusive product. It was notable that 4Z-β-vinyl-α-diazo-β-ketoesters were unstable, and could be isomerized into 4Zi-p-vinyl-a-diazo p-ketoesters.2. One-pot deprotection-oxidation-Wittig reaction of silyl ethers in the presence of an equivalent of acetic acid, MnO2 and stable Wittig reagents generated the corresponding a, p-unsaturated esters. Various silyl ethers, such as benzylic, allylic and alkylic silyl ethers, etc. were examined. Trimethylsilyl ethers and tert-butyldimethylsilyl ethers could be oxidized selectively by MnO2/CH3COOH; however, tetrahydropyranyl ethers could not. It was shown that the pre-existing Z-alkene geometries were retained efficiently. In addition, the problem on the oxidative diol cleavage was overcome.3. DMP-mediated one-pot deprotection-oxidation-Wittig reaction of...