Abstract Acrylonitrile, methyl methacrylate, styrene, methyl acrylate, acrylic acid, and methacrylic acid were found to be polymerized by the system of imidazole and carbon tetrachloride. The polymerization proceeded through radical mechanism. In spite of the presence of carbon tetrachloride, the molecular weight of the polymer obtained was very high. The polymer contained chlorine, and from the reaction product Cl − could be extracted by water. From these results and the data of NMR measurements, an initiation mechanism was proposed. Also some polymers of N‐vinyl compounds, such as poly‐4‐vinylpyridine or poly‐2‐ethyl‐N‐vinylimidazole, were found to be active. However, the initiation mechanism seemed to differ from that by the above imidazole‐carbon tetrachloride system. In the polymerization initiated by imidazole and carbon tetrachloride, various macromolecules, such as cellulose, poly‐N‐vinylpyrrolidone or poly‐N‐vinylcarbazol, could accelerate the polymerization of acrylonitrile. A matrix mechanism is still in question for this interesting reaction.
The electroreduction of Ar-substituted methyl cinnamates in acetonitrile gave all-trans cyclized hydrodimers stereoselectively (58 approximately 90% de). In all cases, small amounts (<10% yield) of meso hydrodimers were also formed. The electrolysis was performed conveniently using an undivided cell at a constant current. The transition states for the hydrocoupling were calculated with semiempirical methods. The all-trans cyclized hydrodimers were transformed to C(2)-symmetric dl-3,4-diaryladipic acids and trans-3,4-diarylcyclopentanones. The chiral auxiliary [(1R)-exo]-3-exo-(diphenylmethyl)borneol, prepared from (1R)-(+)-camphor, was highly effective for the stereoselective hydrocoupling of its cinnamates by electroreduction. From the resulting hydrodimers, (3R,4R)-3,4-diaryladipic acid esters and (3R,4R)-3,4-diarylhexane-1,6-diols were synthesized in 87-95% ee.
The oxidative homocouplings of lithium enolates of (4S)-3-(3-arylpropanoyl)-4-isopropyl-2-oxazolidinones and (4R,5S)-1-(3-arylpropanoyl)-3,4-dimethyl-5-phenyl-2-imidazolidinones gave the corresponding R,R-dimers stereoselectively with TiCl4, PhI(OAc)2, or CuCl2 as an oxidant. The stereoselectivity can be explained by a radical coupling mechanism. Optically active dibenzylbutyrolactone lignans, such as (−)-hinokinin and (−)-dimethylmatairesinol, and dibenzylbutanediol lignans, such as (−)-dihydrocubebin and (−)-dimethylsecoisolariciresinol, were synthesized from the major R,R-dimers. The oxidative coupling of (4R,5S)-1-(3-arylpropanoyl)-3,4-dimethyl-5-phenyl-2-imidazolidinones with LDA−I2 gave R,S-dimers mainly, and this result can be explained by an SN2 mechanism.
We prepared α-substituted carboxylic acids and ethyl esters and studied the effects of these compounds on the growth of lettuce seedlings. Compounds with shorter alkyl chains inhibited growth more than those with longer alkyl chains. α-Phenoxybutyric acid or its ethyl ester at 1 ppm caused as much inhibition as the corresponding unsubstituted acid and its ester at 1000 ppm. An electron-attracting Cl group introduced into the α-phenoxy group caused stronger inhibition than the electron-donating H or CH3 groups. α-Phenoxypropionic acid, α-(2, 4-dichlorophenoxy)-butyric acid, α-(2, 4-dichlorophenoxy) valeric acid, and their ethyl esters might be useful as herbicides and α-(2, 4-dimethylphenoxy) stearic acid and α-phenoxystearic acid might be useful as growth-promoting substances.
The reaction of N-alkoxycarbonyl-1-methoxyamines and (4S)-3-butyryl-4-isopropyl-2-oxazolidinone afforded the corresponding adducts with anti selectively (60% de). Both anti- and syn-α,β-disubstituted β-amino acid methyl esters were obtained in 98% ee from the adducts. The enantiomerically pure precursor for the synthesis of carbapenem antibiotic PS-5 was prepared by this method.
Abstract Der Dicarbonsäureester (I) liefert bei der Acyloin‐Kondensation in Gegenwart von Trimethylchlorsilan den Bis‐trimethylsilyläther (II), der nach Hydrolyse das Acyloin (III) ergibt.
