Wolf rearrangement

Although the Wolf rearrangement of diazoketones in the presence of silver benzoate and triethylamine in methanol could involve rearrangement of an intermediate diradical or carbonium ion conjugate... 

Pyrazolo[5,l-c]-l,2,4-triazoles (242) are obtained by photochemical Wolf-rearrangement of 239 in ethanol (79JHC195) 240 and 241 are assumed intermediates. 

The starting 1,2,3-thiodiazole is formally equivalent to a diazoketone and the first part of the reaction is the same as the photocatalyzed Wolf rearrangement. 

Appropriately substituted diazo ketones have been converted into oxetanes in two instances by Wolf rearrangement processes. The structure of compound (52) was established by X-ray crystallography (69MI51300, 81CSC345). Reaction of 4,4-dibromo-2,2,5,5-tetramethyltetrahydro-3-furanone with aqueous base is a good method of preparation for 3-hydroxy-2,2,4,4-tetramethyloxetane-3-carboxylic acid (equation 90) (66JA1242). 

To Open-Chained Compounds (+ C,C-Rearrangements) (Wolf—Rearrangement)... 

When ethyl trimethylsilyldiazoacetate (la) is photolyzed with a high-pressure mercury lamp in alcohols, four products (2-5) are obtained. Products 2 and 3 may be rationalized in terms of insertion reaction of trimethylsilyl carboethoxycarbene and product 4 has been explained by a Wolf rearrangement. 

The commercial positive photoresists are based on the photoinduced Wolf rearrangement of a diazoquinone to a indene carboxylic acld ... 

It may be worthwhile mentioning that most of the arguments in the development of the Woodward-Hoffmann rules have been substantiated with the results of EH calculations 4>83). Other EH molecular orbital studies were devoted to the elucidation of the mechanism of the Wolfe rearrangement 84>, and to the investigation of the hydrolysis of acetylcholine 85>. A simplified form of the EH method has been used to determine the role of non-classical ions in 1,2 rearrangements 86>. 

Wolf rearrangement, 7, 193 pyrylium salt synthesis from, 3, 871... 

The first step in the reaction scheme involves the elimination of nitrogen from the diazoquinone (VI), forming a carbene (VII). The carbene undergoes a Wolf rearrangement, involving ring contraction, and leading to the formation of ketene (VIII). In the presence of small amounts of water in the novoiac binder," hydration of the ketene leads to the formation of indene carboxylic acid (IX). The main feature of the process is the transformation of a fairly hydrophobic... 

Novolaks are phenol-formaldehyde type polymers. Novalaks are synthesised via a polycondensation reaction which is halted before the polymer becomes fully cross-linked. As Novalak polymers contain phenol units, they have reasonable solubility in aqueous base solutions. To act as a positive tone resist, the solubility of the Novolak polymer in basic solutions must be greatly enhanced. This can be achieved by using photochemically reactive additives. The additive used is a diazoanthraquinone, which undergoes a photochemically driven Wolf rearrangement reaction to produce a carboxylic acid (Scheme 13.4). 

In the generation of diphenylketene from phenylbenzoyldiazomethane in the presence of styrene, both the cycloadduct and the linear adduct, Ph2CHCOCH=CHPh, are obtained Intramolecular cycloaddition of ketenes, generated by photolysis or thermolysis of diazoketones, to bonds are also known. For example, photolysis of the bicyclic diazoketone 139 affords the bicyclic ketone 143, resulting from intramolecular cycloaddition of the ketene intermediate 141. As a byproduct, the tetracyclic ketone 142 is formed by addition of the ketocarbene 140, prior to the Wolf rearrangement. ... 

The Wolf rearrangement of N -Boc-/Z-protect aminodiazoketones in the presence of silver benzoate under microwave irradiation has been described. The reaction is found to be rapid, efficient and complete. Verma (2002) observed that the microwave irradiation technique has been used to decrease the time neeessary to carry out cleaner reaction with higher selectivity and easier work up. A sample, rapid, and efficient route for the preparation of several amino acid benzyl ester p-toluenesul-fonate and hydrochloride salts under microwave irradiation was also demonstrated by Patil et al. (2002). 

Sudrik et al. (2002) have studied the specific Wolf rearrangement of 3-Diazocamphor in the presence of benzylamine under microwave irradiation. 

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