Diazonium salts with Grignard reagents

G. Reaction of Diazonium Salts with Grignard and Related Reagents. 307... 

The reaction of diazonium salts with carbanions in protic solvents (Japp-Klingeman reaction) is well known. It has now been reported that Grignard reagents derived from aromatic or tertiary bromides are converted into azocompounds with substantial improvement in yields, by a modified procedure. 

Grignard reagents and diazonium zinc chloride double salts have been used to prepare azo compounds. The reaction of arylzinc chloride with a diazonium salt has also been used. By this means, mixed aromatic-aliphatic azo compounds have been prepared. 

Variable yields of azo compounds were also obtained from reactions of Grignard reagents with diazonium salts, but benzenediazonium tetrafluoroborate gave acceptable yields from arylmagnesium bromides or t-butylmagnesium chloride in THF [19] ... 

Hydrazines may also be obtained via amidocuprates (Eq. 47)54 but the yields are low. Addition of Grignard reagents to diazonium salts provides azo compounds, which may be reduced to hydrazines. Yields in the former reaction are often low and the requirement to use dry diazonium salts adds a potential hazard. The best yields are obtained with o-benzenedisulfonimide salts (Eq. 48).191... 

Synthesis of aldehydes by formylation of Grignard reagents with p-dimethylaminobenzaldehyde and a diazonium salt (see 1st edition). 

Azidobenzo[6]thiophenes are prepared via the corresponding diazonium salts, by treatment of a Grignard reagent with toluene-p-sulfonyl azide and sodium pyrophosphate360 or from organolithium derivatives (Section V). 

In addition to diazonium salts, there are many other species that are able, once electrochemicaUy activated, to modify the surface with aromatics, unsaturated and saturated groups. These surface modifications can be achieved by (i) oxidation (amines, hydrazines, alcohols, carboxylates, carbamates, carbanions, Grignard reagents) (ii) reduction, some being closely related to diazonium salts (iodoniums, sulfonium) and other different species (vinylics, alkyl halide) (iii) spontaneously, chemically or pho-tochemically (alcenes, azides, peroxides). Note that electrochemical oxidation methods can be applied only to the materials that can withstand quite positive potentials such as carbon or Pt. This section will describe these modifications [357]. 

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