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Vol 476, No 2 (2017)
- Year: 2017
- Articles: 2
- URL: https://journals.rcsi.science/0012-5008/issue/view/9277
Chemistry
Synthesis of functionally substituted benzaldehydes
Abstract
A new method of synthesis of functionally substituted benzaldehydes by catalytic debromometoxylation of dibromomethylarenes with benzaldehyde dimethyl acetal has been suggested. Anhydrous zinc chloride has been used as a catalyst. Being soft Lewis acid, it formed no strong complex with aldehyde group and other functional groups. The initial acetal has been readily recovered by the treatment of benzaldehyde isolated from the reaction mixture with trimethyl orthoformate.
227-229
Structure and fluxional behavior of pentamethoxycarbonylcyclopentadiene
Abstract
Quantum-chemical calculations by the density functional theory method at the B3LYP/6- 311++G** level have shown that the fulvene form of pentamethoxycarbonylcyclopentadiene 1 in the gas phase is more favorable in energy than cyclopentadiene form 2 by ΔEZPE = 7.8 kcal/mol. The fluxional behavior of fulvene 1, detected by dynamic NMR can be explained by the mechanism of circular low-barrier 1,9-O,O'-H shifts accompanied by rotations of the hydroxymethoxymethylene substituent about the С=С bond with the activation barrier ΔEZPE= 23.5 (gas) and 20.9 (CH2Cl2) kcal/mol. This reaction path is 18.6 kcal/mol more favorable in energy than transition of fulvene 1 to cyclopentadiene 2 with subsequent 1,5- sigmatropic hydrogen shifts in the five-membered ring.
230-234