Polarized ethylene. V. Synthesis of 1-substituted indolizine,pyrazolo[1,5-a]pyridine,and their related compounds using methoxyethylene derivatives

The reaction of pyridinium or isoquinolinium N-ylides with methoxy-substituted ethylenes gave the corresponding indolizine and pyrrolo[2,1-a]isoquinoline derivatives bearing acetyl, aroyl, cyano, ester group at the 1-position in one step. Pyrazolo[1,5-a]pyridine, pyrazolo[1,5-a]quinoline, and pyrazolo[5,1-a]isoquinolines were also synthesized in good yields from the corresponding aromatic N-imines and methoxyethylene derivatives.     

Diels-Alder cycloadditions of 2(1H)-quinolones having an electron-withdrawing group at the 3-position acting as dienophiles with dienes.

Diels-Alder cycloadditions of 2(1H)-quinolones having an electron-withdrawing group at the 3-position with alkyl- and silyloxy-1,3-butadienes (2a,b) were carried out to give phenanthridones richly functionalized regio- or stereoselectively under conditions of atmospheric and high pressure. Furthermore, regioselectivity and chemoselectivity of 3-substituted 2(1H)-quinolones to 2a, b were examined using MO calculation.     

An intramolecular charge/electron transfer chemiluminescence mechanism of oxidophenyl-substituted 1,2-dioxetane

The chemiluminescence (CL) mechanism of oxidophenyl-substituted 1,2-dioxetane was investigated by performing TD-DFT calculations on biradicals of three model compounds. We propose a novel mechanism of CL in which excitation of a dissociative intermediate by infrared radiation (IRE) of the surrounding solvent is considered. The excitation energies and oscillator strengths (f-values) were estimated for intermediates along the reaction coordinate (Rx). The difference in efficiencies of CL between syn- and anti-isomers of m-oxidophenyl-dioxetane is explained using the difference in potential curves of the singlet excited states (S) and the IRE mechanism. At the point where the biradical of the anti-isomer decomposes into two fragments, the interaction between the S and triplet (T) states is induced by a significant back electron transfer (BET) from the dioxetane group to the oxido-phenyl group and the S(1) excited state is stabilized and CL efficiency is enhanced. In the syn-isomer, the barrier in the S(1) potential curve to reach the final CL state is higher than for the anti-isomer, which reduces the efficiency. The poor CL yield for the p-isomer is ascribed to a much higher barrier in the potential curve of the S(1) state.     

Significant solvent effects and unusual additions of p-chloranil in the photoinduced electron-transfer reaction of 2,2-dianisyl-4-isopropylidene-3,3-dimethylcyclobutanone

A photoinduced electron-transfer reaction of 2,2-dianisyl-4-isopropylidene-3,3-dimethylcyclobutanone (1) in benzene gave two unexpected CA-adducts, 5,5-dianisyl-4,4-dimethyl-3-[1-(4-hydroxy-2,3,5,6-tetrachlorophenyl)methylethylidene]dihydrofuran-2-one (7) and 2,2-dianisyl-4-(4-hydroxy-2,3,5,6-tetrachlorophenoxy)-4-isopropenyl-3,3-dimethylcyclobutanone (8), while the reaction in acetonitrile did not, suggesting significant solvent effects on the product distribution.     

Use of shift reagent with diastereomeric MTPA esters for determination of configuration and enantiomeric purity of secondary carbinols in 1H NMR spectroscopy

The relative magnitude of the lanthanide induced shift(LIS)_by Eu(fod)₃ for ¹H NMR spectra of the OMe group of diastereomeric (R)-(+)-α-trifluoromethylphenylacetate esters [(R)-(+)-α-methoxy-α-trifluoromethylphenylacetate esters [(R)-(+)-MTPA esters (3)] of thirty-two secondary carbinols have been measured. There is a regularity in the relative magnitudes of the LIS values of the OMe signals of the alternate diastereomers which can be correlated with their absolute configurations. This constitutes a versatile method for assigning absolute configurations to secondary carbinols. Furthermore, the relative intensity of the OMe signals can be used for determination of the composition of these diastereomeric MTPA esters and thus the enantiomeric carbinols from which they are quantitatively prepared. These studies extend the usefulness of MTPA derivatives in stereochemical studies.