Phenylhy drazones

In addition to direct inhibition of the vesicular transport protein, storage of neurotransmitters can be reduced by dissipation of the proton electrochemical gradient. Bafilomycin (a specific inhibitor of the vacuolar H+-ATPase), as well as the proton ionophores carbonyl cyanide m-chlorophenylhydrazone (CCCP) and carbonylcyanide p-(trifluoromethoxy) phenylhy-drazone (FCCP) are used experimentally to reduce the vesicular storage of neurotransmitters. Weak bases including amphetamines and ammonium chloride are used to selectively reduce ApH. 

A variety of systems are known in which there are observable crystal-field effects on the configuration about a double bond. Thus, acetaldehyde phenylhy-drazone occurs in solution as an equilibrium mixture of syn and anti forms (in benzene the ratio is 3 2), but in the crystal only the anti isomer is found (60). 

Similar spectral changes were also observed for alkaline solutions of inosose phenylhydrazones and phenylosazones. For example, 2,4,6/3,5-pentahydroxycyclohexanone phenylhydrazone (mt/o-inosose-2-phenylhy-drazone) [0.1 mM, AmaxMe2S0 282 and 304 (sh) nm] in alkaline methyl sulfoxide solution gave a band at 445 nm (with rapidly changing intensity), also associated with the diminution of the paramagnetic species this band was replaced by a new band at 382 nm. Similar behavior was observed with other inososes. 

The ketone component can be replaced by cyclic enol ethers, which react with phenylhydrazines to give phenylhy-drazones, as has been demonstrated by a large-scale synthesis of 5-fluorohomotryptophol derivatives from 4-fluorophe-nylhydrazine hydrochloride and tetrahydropyran <19970PD300>. The Grandberg modification of the Fischer synthesis involves the use of an acetal as the ketone equivalent <2001T1041>. 

In a Fischer synthesis, the formation of the hydrazone and its cyclization to the indolenine in the crude reaction mixture can be monitored conveniently by IR spectra. The ketone C=0 absorption near 1720 cm 1 disappears as the phenylhy-drazone C=N absorption in the 1625-1640 cm 1 region appears, which in turn is replaced by the indolenine C=N absorption at 1570-1580 cm-1. If a Fischer s base is formed directly, the IR spectrum exhibits two peaks near 1615 and 1650 cm 1. All these absorption peaks are strong and sharp. 

The dimethylaminomethylene compound 468 was converted to arylamino-methylene derivatives 471 with anilines in acetic acid, and to the phenylhy-drazone 472 with phenyldiazonium chloride (83JCR(S)161 84JMC1253). The ester group of compounds 471 and 472 could be hydrolyzed to a carboxylic group under alkaline conditions (84JMC1253). 

Borsche-Drechsel cyclization. Acid-catalyzed rearrangement of cyclohexanone phenylhy-drazone to tetrahydrocarbazole. Subsequent oxidation yields carbazole. 

Other Electrophiles. In addition to carbonyl compounds, ester enolate (1) also reacts with other electrophiles. With nitrones, the product is dependent upon the structure of the nitrone a,N-dialkyl nitrones provide alkenes, while a-aryl-A-alkyl nitrones or aW-diaryl nitrones usually give aziridines. With the phenylhy-drazone of a 1,2-dicarbonyl compound, reaction with (1) provides a convenient preparation of 3(2f/)-P3 dazinones (eq 3). ... 

Courtot, R, Pichon, R., and Le Saint, J., Photochromise par isomerization syn-anti de phenylhy-drazone-2 de tricetones-1,2,3 et de dicetones-1,2 substituees, Tetrahedron Lett., 1181, 1976. 

---