A ring substitutions

Via such a gas/liquid reaction, toluene-2,4-diisocyanate reacts with chlorine to give l-chloromethyl-2,4-diisocyanatobenzene [6], As a ring-substituted side product, toluene-5-chloro-2,4-diisocyanate is formed in minor quantities. 

Fenfluramine, like MDMA and MDA, is a ring-substituted amphetamine derivative that has been found to meet all the criteria for neurotoxicity. 

Second-order rate constants A for the replacement of a ring-substituted benzoate group by hydroxide ion in a number of complexes (base hydrolysis) have been carefully determined at 25°C in 40% aqueous methanol ... 

There appeared to be a good correlation between the mouse toxicity data from an I.P. route and the rat feeding study (Appendix II). With the results from these tests we were able to define the "A" ring substitution requirements required to make the trinitro diphenyl amines toxic to rats. 

There are a number of reactions related to the photo-Fries process, in which cleavage of a bond adjacent to a heteroatom ring substituent leads by way of radical intermediates to a ring-substituted product. As an illustration, N-phenylcaprolactam, which can be regarded as... 

Triply bridging orf/io-phenylene complexes sometimes arise in curious ways. In the reaction of Os3(CO)10(MeCN)2 with salicylaldehyde benzy-limine one would naively expect that coordination would be through N and O atoms as with other metal systems. The first formed compound (40, Scheme 6) results from ortho metallation while, of the three isomeric decarbonylation products (41 to 43), compound 43 contains only Os—C bonds to the ligand and is a ring-substituted version of Os3H2(C6H4)(CO)9 (Scheme 6) (237). 

The main flavonoid skeleton derives from the stepwise condensation of three molecules of malonyl CoA with one molecule of 4-coumaroyl CoA, a reaction catalyzed by chalcone synthase (CHS) to form naringenin (2, 4,4 ,6,-tetrahydroxy) chalcone, the common intermediate in the formation of all flavonoids with 5,7-dihydroxy (flavone numbering) A-ring substitution. In some plants, however, an NADP-dependent chalcone-ketide reductase coacts with CHS to form 6 -deoxychalcone, the precursor of 5-deoxyflavonoids. The resulting chalcones undergoe a stereospecific cyclization to the corresponding (2S) flavanones, the... 

The two aryl rings in the benzhydryl cation [22C ] are also known to be twisted equivalently from the cationic sp plane by ca. 16.0° according to ab initio optimization at the RHF/6-31G level. While equivalent rotation of the X-aryl ring must be the cause of the reduced resonance demand, especially in the case of equivalently disubstituted benzhydryl cations [22C (X = Y)], the symmetry will be destroyed by replacing one phenyl ring by a ring substituted by an ED Y-substituent the Y-substituted phenyl ring will become more nearly coplanar with the sp cationic carbon and this will enhance the tt delocalization. The electronic demand will therefore be reduced on the other,... 

From the table on p. 112 it will be seen that when a ring-substituted aniline has the para position to the amino group unoccupied, mercury invariably enters that position. A similar statement holds for the ortho position to the amino group, but should these two be filled, the mercury may enter the C position, if vacant. 

A further case, discussed by Walling, Seymour and Wolfstirn (25), is represented by the terpolymerization of maleic anhydride with alpha-methylstyrene and a ring-substituted alpha-methylstyrene. 

Sometimes a cathodic substitution reaction takes place during the reduction of o-substituted nitrobenzenes thus, the reduction of 2-nitrophenoxyacetic acid [52] in 2 A hydrochloric acid (50% ethanol) yielded 5-chloro-2i7-l,4-benzoxazin-3(4H)-one rather than the expected cyclic hydroxamic acid [52]. In the presence of another nucleophile Y (e.g., thiocyanate), a ring substitution with this reagent occurs. 

The even more sterically hindered Grignard reagent, fcrr-butylmagnesium bromide, reacts with benzophenone (Scheme 5) to give a ring-substituted product in high yields [2b,9] in a very fast reaction. 

This method has been also apphed to the synthesis of a novel class of confor-mationally restricted glutamates with a ring substitution pattern similar to the kai-noid group of amino acids. In all arylations a diastereomeric mixture was obtained preferential addition of the aryl group to the exo face was predominant (Scheme 13.7) [35]. 

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