Hydrazones conversion

Hydrazine derivatives, reduction 68 Hydrazones, conversion to primary amines 69 oxidation 710... 

Hexafluoroacetone imine distilled slowly during ca. 1 hr. into stirred anhydrous hydrazine cooled below 10°, allowed to warm to room temp., poured rapidly on P2O5, mixed and distilled -> hexafluoroacetone hydrazone (Conversion 53-59%) dissolved in benzonitrile, added dropwise with stirring during 1 hr. under Ng to ice-cooled Pb-tetraacetate and benzonitrile, then stirred 1 hr. at room temp. bis(trifluoromethyl)diazomethane (Y 76-79%). F. e. s. W. J. Middleton and D. M. Gale, Org. Synth. 50, 6 (1970). 

Inspired by the work of Burk and Feaster ) we attempted to use (2-pyridyl)hydrazine (4.36) as a coordinating auxiliary (Scheme 4.10). Hydrazines generally react effidently with ketones and aldehydes. Hence, if satisfactory activation of the dienophile can be achieved through coordination of a Lewis acid to the (2-pyridyl)hydrazone moiety in water. Lewis-add catalysis of a large class of ketone- and aldehyde-activated dienophiles is antidpated Subsequent conversion of the hydrazone group into an amine functionality has been reported previously by Burk and Feaster ... 

Okfm Syntheses. Conversion of aldehydes and ketones to olefins by the base-catalyzed decomposition of -toluenesulfonic (Ts) acid hydrazones (10) is known as the Bamford-Stevens reaction (54,55). 

Hydroxybenzaldehyde has extensive use as an intermediate in the synthesis of a variety of agricultural chemicals. Halogenation of Nhydroxybenzaldehyde, followed by conversion to the oxime, and subsequent dehydration results in the formation of 3,5-dihalo-4-hydroxybenzonitrile (2). Both the dibromo- and dhodo-compounds are commercially important contact herbicides, hromoxynil [1689-84-5] (2) where X = Br, and ioxynil [1689-83-4]( where X = I respectively (74). Several hydrazone derivatives have also been shown to be active herbicides (70). 

Special reactions of hydrazides and azides are illustrated by the conversion of the hydrazide (205) into the azide (206) by nitrous acid (60JOC1950) and thence into the urethane (207) by ethanol (64FES(19)105Q) the conversion of the same azide (206) into the N-alkylamide (208) by ethylamine the formation of the hydrazone (209) from acetaldehyde and the hydrazide (205) and the IV-acylation of the hydrazide (205) to give, for example, the formylhydrazide (210) (65FES(20)259). It is evident that there is an isocyanate intermediate between (206) and (207) such compounds have been isolated sometimes, e.g. (211). Several of the above reactions are involved in some Curtius degradations. 

Lead tetraacetate is often used as the oxidizing agent for the conversion of hydrazones into ring-fused systems. 

Clean examples of diaziridine to hydrazone rearrangements are rare. Diaziridine (119) mentioned above rearranges to the isomeric enhydrazone in boiling toluene, and 2,4-dinitrophenyldiaziridine (125) under the same conditions affords the 2,4-dinitrophenylhy-drazone (145) within 4 h. On blocking this rearrangement by iV-methyl, conversion with loss of cyclohexanone occurred to give benzotriazole iV-oxide (146) (72JOC2980). 

BAMFORD - STEVENS - CAGUOTI- SHAPIRO Olelinalwn Conversion o( ketones to olelins via tosyl hydrazones with NaOR, LAH, LDA or BuLi... 

SMITH MIDDLETON RQZEN Fhionnation Conversion ol carbonyls to CF2 compounds by SF4 (Smith) or dielhylammosullur Influonde (OAST) (Middleton) or by IF on hydrazones (Rozen)... 

Table 6. Conversion of Aryl Hydrazones to Geminal Difluorides...

Evidently, analogously to the mentioned cyclization of similar oximes to ben-zisoxazole derivatives (See Section II.A), reaction can take place only in compounds with suitable configuration. However, in case of hydrazones, due to the tautomeric equilibrium of both possible configurations, the reaction usually achieves complete conversion. The usual setup involves heating with the respective hydroxide if an ester group is present, it is partially or completely hydrolyzed to the corresponding acids, which, in addition, can also undergo decarboxylation. 

When present in macro quantities, aldehydes and ketones can be determined by conversion to the 2,4-dinitrophenylhydrazone which can be collected and weighed. When present in smaller quantities (10 3M or less), although hydrazone formation takes place, it does not separate from methanol solution, but if alkali is added an intense red coloration develops the reagent itself only produces a slight yellow colour. Measurement of the absorbance of the red solution thus provides a method for quantitative determination. 

Note. The mundane procedures for conversion of quinoxalinecarbaldehydes into their oximes, hydrazones, semicarbazones, acetals, Schiff bases, and the like are often used but seldom described. Accordingly, only a few typical examples are given here. 

Most resolution is done on carboxylic acids and often, when a molecule does not contain a carboxyl group, it is converted to a carboxylic acid before resolution is attempted. However, the principle of conversion to diastereomers is not confined to carboxylic acids, and other groupsmay serve as handles to be coupled to an optically active reagent. Racemic bases can be converted to diastereomeric salts with active acids. Alcohols can be converted to diastereomeric esters, aldehydes to diastereomeric hydrazones, and so on. Even hydrocarbons can be converted to diastereomeric inclusion... 

SO the product in this case is also the hydrazone, and not the azo compound. In fact, compounds of the type 16 are seldom isolable from the reaction, though this has been accomplished. The cleavage step shown is an example of 12-41 and, when a carboxyl group cleaves, of 12-38. The overall process in this case is called the Japp-Klingemann reaction and involves conversion of a ketone (17) or a carboxylic... 

The addition of KCN to triisopropylbenzenesulfonyl hydrazones (53) provides an indirect method for achieving the conversion RR CO RR CHCN. " The reaction is successful for hydrazones of aliphatic aldehydes and ketones. 

Figure 26.2 Heat profile and conversion of the benzophenone hydrazone and of the hexylamine for a competitive amination reaction involving 3-bromobenzotrifluoride (0.5 M), benzophenone hydrazone (0.25 M) and hexylamine (0.25 M). Temperature 90°C.

The heat profile shows that the reaction has zero order kinetics at first, and then switches to positive order kinetics. The benzophenone hydrazone reacts first only when it is completely consumed, the reaction involving hexylamine begins. Samples were taken and analyzed by and NMR. One sample was taken when the aryl halide conversion was low, at about 5%, and the profile was overall zero order the second when the profile had switched to positive order and the conversion of the halide was greater than 50%. 

Watanabe reports a new method for the direct conversion of o-choroacetaldehyde N,N-disubstituted hydrazones into 1-aminoindole derivatives 93 by palladium-catalyzed intramolecular ring closure of 92 in the presence of P Bu3 or the bisferrocenyl ligand 94 <00AG(E)2501>. When X = Cl, this cyclizative process can be coupled with other Pd-catalyzed processes with nucleophilic reagents (e.g., amines, azoles, aryl boronic acids) so as to furnish indole derivatives with substituents on the carbocyclic ring. 

Precursors for this task were obtained by addition of /-butylmagnesium bromide to the central bond of [1.1.1 ]propellane 40a followed by conversion of the 3-f-butylbicyclo[ 1.1.1 Jpentyl-1 -y 1-magnesium bromide (88) into the ketones 89 by standard methods.27 Reaction of ketones 89 with tosyl hydrazide afforded the hydrazones 90, which gave the corresponding lithium salts 91 by reaction with MeLi in ether. These salts were dried under high vacuum and then pyrolized at 4 x 10 5 torr in the temperature range of 100-130°C and the volatile products condensed in a liquid nitrogen-cooled trap. 

---