Aryl triazene

With primary and secondary aryl amines a reaction at the amino nitrogen can occur, leading to formation of an aryl triazene 5 ... 

Rearrangement of aryl triazenes can be used to prepare azo derivatives of primary and secondary aromatic amines." These are first diazotized at the amino group (see 11-4) to give triazenes, which are then rearranged by treatment with acid. The rearrangement always gives the para isomer, unless that position is occupied. 

Caution All 1 -aryl triazenes are toxic and direct hand contact should be avoided. The checkers used hexane for the recrystallization. 

The Wallach reaction, the thermal decomposition of an aryl triazene (Scheme 46), has also been attempted as an alternative to the Balz-Schiemann reaction [54,220,221]. Although a wide variety of experimental conditions have been tried, the radiochemical yields remain low. 

Two linkers based on the triazene chemistry have been developed. While the Tj linker system consists of 3,3-dialkyl-l-aryl triazene bound to... 

Since dialkyltriazenes were first used in aromatic fluorination by Wallach, ° many fluoroaro-matic compounds have been obtained in high yield by the decomposition of 3,3-dialkyl-l-aryl-triazenes with various fluorides in acidic media (see Vol. ElOa, p 725fT). Aryltriazenes are a potential source of aryldiazonium salts under controlled, mild, acid conditions. Therefore, this replacement (Route A) can be considered as a type of Balz-Schiemann reaction (see Section... 

Reaction 8 is the obvious primary reaction and is entirely analogous to the known decomposition of aryl triazenes. 

For example, the triazene (228) is obtained from ditizotized anthra-quinone and ammonium carbonate under these conditions " (equation 115). Further, the formation of aryl azides by oxidation of aryl triazenes with hypochlorite solution has been reported In a related... 

Further reductions of 17-hydroxy-17-alkynyl-steroids with LiAlH4-AlCl3 to give the 17(20),20-dienes (allenes) confirmed that the reactions proceeded by a stereospecific c/5-5n2 mechanism. Aromatic fluorides were prepared in high yield by treatment of aryl-triazenes with 70% HF in pyridine and 4-fluoro-oestrone methyl ether was prepared by this method. ... 

The first critical objective in this campaign was finding a method to convert the aryl triazene into a phenol, since its mission in directing the formation of both bisaryl ether systems was now complete. Although model studies indicated its relatively facile removal, this motif unfortunately proved far more resilient within the context of 93 as direct techniques to effect its transformation into a phenol under various acidic conditions universally failed, leading only to reduced product (i. e. a hydrogen atom instead of the triazene... 

Alkyl aryl triazenes provide an alternative reagent for alkylation of acids via alkyl diazonium ions. The triazenes are stable crystalline materials that can be stored. Reaction with carboxylic acids occurs rapidly to afford the corresponding ester... 

The T1 linker system consists of 3,3-diaIkyl-l-aryl triazenes boimd to the support via the alkyl chain (either via a dibenzyl type or a piperazinyl type anchoring). The T2 Unker family is based on immobilized arene diazonium salts [228-231]. 

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