Solvable lattice models whose states are dominant integral weights of A it−1 (1)

A new hierarchy of solvable IRF models is presented. It is generated from Belavin's Z _n ×Z _n symmetric model. The site variables take values in the set of level l dominant integral weights of A _–1 ⁽¹⁾ . It is conjectured that the local state probabilities are given through the irreducible decomposition of characters for the affine Lie algebra pair (A _n–1 ⁽¹⁾ A _n–1 ⁽¹⁾ ,A _n–1 ⁽¹⁾ ).     

Triplet diphenylcarbenes protected by o-Aryl groups

Diphenyldiazomethanes (2a-N(2)) having phenyl groups at the ortho positions were prepared and the corresponding diphenylcarbenes (2a) photolytically generated from them were characterized not only by the traditional product analysis method but also by ESR and UV/vis spectroscopy in a rigid organic matrix at low temperature and in laser flash photolysis in solution at room temperature. Product analysis indicated that fluorenes 4a are formed almost exclusively. Fluorene is most likely produced by the attack of singlet carbene (1)2a on an ortho carbon of the phenyl substituent to generate isofluorene, followed by 1,5-H shift. Irradiation of 2a-N(2) in a 2-methyltetrahydrofuran (2-MTHF) matrix at 77 K gave ESR signals ascribable to triplet carbenes ((3)2a). UV/vis spectra of (3)2a were obtained by irradiating 2a-N(2) under identical conditions. However, laser flash photolysis (LFP) of 2a-N(2) in degassed benzene at room temperature showed transient absorption bands completely different from those observed in photolysis in the 2-MTHF matrix at 77 K. The transient band decayed in first-order with a rate constant of 7.6 x 10(4) s(-1), which was not retarded by deuterium substitution of o-phenyl hydrogens. Essentially the same transient band was observed in LFP of fluorene 4a. The LFP of 2a-N(2) in nondegassed benzene gave transient absorption bands ascribable to triplet carbene (3)2a and the corresponding carbonyl oxide. The quenching rate constant of (3)2a by oxygen and the lifetime of (3)2a in the absence of oxygen were estimated by plotting the observed pseudo-first-order rate constant of the formation of the carbonyl oxide against the concentration of oxygen. They were 1.9 x 10(7) M(-1)s(-1) and 16 micros, respectively. Similar studies with diphenyldiazomethanes having a series of substituents (4-Ph, 3,5-(CF(3))(2), and 2-F) on the ortho-phenyl rings gave essentially identical results, indicating that those substituents exhibit little effect on overall reaction pathway. From those studies, it is suggested that triplet carbenes (3)2 are also trapped by the ortho-phenyl ring to give eventually fluorenes.     

Syntheses of benzomorphan and related compounds. Part III. An alternate synthesis of 3-substituted-1,2,3,4,5,6-hexahydro-8-hydroxy-2,6-methano-6,11-dimethyl-3-benzazocine

Reduction of the appropriate Schiff bases gave 5-benzylamino-3-methyl-2-pentene (XVII) and l-benzylamino-3-methylpentane (XVIII), the condensation of which with methyl 3-(4-methoxyphenyl)-2,3-epoxypropionate afforded a mixture of the isomeric 1-benzyl-2-(4-methoxy-benzyl)-3,4-dimethyl-4-hydroxypiperidines (XIXa and XIXb). The piperidinols were heated with hydrobromic acid, respectively, to afford 3-benzyl-1,2,3,4,5,6-hexahydro-8-hydroxy-2,6-methano-6,11-dimethyl-3-benzazocine (II). Since the conversion of II to pentazocine (Ic) had already been accomplished, an alternate synthesis of Ic was achieved.     

Inhibitory effects of catechol derivatives on arachidonic acid-induced aggregation of rabbit platelets

Pyrocatechol and other non-substituted dihydric phenols, which have strong redox power, inhibited arachidonic acid-induced aggregation of rabbit platelets at much lower concentrations than those at which these phenols inhibited stable prostaglandin endoperoxide, U46619-induced aggregation. Among non-substituted dihydric phenols, pyrocatechol was most potent. In order to clarify the physicochemical properties of the phenolic compounds which control the inhibitory potencies of dihydric phenols, we observed the inhibitory effects of 3- and 4-substituents of pyrocatechol on arachidonic acid-induced platelet aggregation. Among seven derivatives tested, the inhibitory effect of 4-C6H5-substituent was strongest and 4-COOH-substituent was weakest. Inhibitory effects of the catechol derivatives were well correlated with the quotients of their hydrophobicities and oxidation-reduction potentials. Inhibitory effects of hydroquinone and resorcinol were also on the same correlation line. These results suggest that the inhibitory effects of catechol derivatives and other dihydric phenols are controlled by two physicochemical properties: oxidation-reduction potential and hydrophobicity.     

Kinetics of deactivation of Pd/C catalyst repeatedly used in the liquid-phase hydrodechlorination of PCE

The deactivation kinetics of the Pd/C catalyst used in the catalytic hydrodechlorination of PCE in either MeOH or 50/50 water-MeOH mixture with catalyst and solvent reuse was investigated. Empirical power-expressions were used to approximate the experimental data.     

Quintet bis(carbene) from triplet diarylcarbenes introduced at the 1,8-position of anthracene

[9-(10-phenyl)anthryl](4-bromo-2,6-dimethylphenyl)diazomethane was found to be stable enough to survive Sonogashira coupling reaction conditions and was converted to [9-(10-phenyl)anthryl](4-trimethylsilylethynyl-2,6-dimethylphenyl)diazomethane, which was reacted with 1,8-diiodoanthracene to give bis(diazo) compound. Bis(carbene) generated by irradiation of the bis(diazo) compound generated a fairly persistent S = 2 quintet state. [structure: see text]     

On the mechanism of the reaction of organosilicon hydrides with dichlorocarbene generated from sodium trichloroacetate

The reaction of sodium trichloroacetate with various organosilicon hydrides in 1,2-dimethoxyethane was investigated and the products, α-triorganosilyldichloromethanes, were formed in yields of 20–50%. The relative rate constants of these hydrosilanes in such insertion reactions of dichlorocarbene were determined by means of competition reactions. The relative reactivities of a series of alkyl substituted hydrosilanes correlate well with the Taft σ* constants for the substituents on silicon, with a ?* value of ?1.07, and a series of aryl substituted hydrosilanes also shows good linear correlation of the log k_rel values with Taft σ* constants, giving ?* value of ?1.18. The hydrogen isotope effect in the reaction, k_H/k_D 1.26 ± 0.02. Based on the observed results, it was concluded that the insertion of CCl₂ into the SiH bond proceeds by a three-center concerted process in which charge separation in the transition state is not large, as suggested by Seyferth for the related PhHgCCl₂Br/XC₆H₄SiMe₂H reactions.     

First total syntheses of the phytotoxins solanapyrones D and E via the domino Michael protocol

The phytotoxins solanapyrones D (1) and E (2) have been synthesized from the decalone prepared by the domino Michael reaction of the kinetic enolate of optically pure acetylcyclohexene with methyl crotonate. The decalone was transformed into a solanapyrone core by equilibration into thermodynamically stable trans-decalone (11), dehydroxylation, and dehydration. Condensation of a methyl acetoacetate equivalent followed by cyclization installed a pyrone moiety. Introduction of a formyl or hydroxymethyl unit into the pyrone ring via Pummerer related reactions furnished solanapyrones D (1) and E (2).     

Studies on the syntheses of heterocyclic compounds. CDXCI pyrimidine derivatives V. Abnormal condensation products of 4-amino-6-chloro-2-methoxypyrimidine with p-nitrobenzenesulfonyl chloride

Condensation of 4-amino-6-chloro-2-methoxypyrimidine (I) with p-nitrobenzenesulfonyl chloride (II) gave, in addition to 6-chloro-2-methoxy-4-(p-nitrobenzenesulfonamido)pyrimidine (III), two abnormal by-products, the structures of which were assigned as 1 -[2-methoxy-4-(p-nitrobenzenesulfonamido)pyrimidine-6-yl]pyridinium N,N-betaine (IV) and N-(p-nitrobenzene-sulfonyl)-β-ureido-β-pyridinium acrylamide N,N-betaine (V).