Tiffeneau reaction

As the reagents used for the process in Scheme 7-48 are different from those in Tiffeneau reactions, and the intermediate 7.141 is not stable enough to be detectable, this process should not be called a Tiffeneau rearrangement. 

This reaction is related to the Nametkin Rearrangement, Retropinacol Rearrangement, Tiffeneau Reaction, and Wagner-Meerwein Rearrangement. 

Asymmetrically substituted rings can expand in two ways to give position isomers, the proportions of which can usually be rationalised by conformational considerations as to which ring bond is suitably placed for migration (however, see reaction 15). Demjanov-Tiffeneau reactions can be applied to bicyclics (reaction 15)... 

The Tiffeneau reaction possesses two properties favouring ring expansion ... 

When a cyclic /3-amino alcohol—e.g. 1—is treated with nitrous acid, a deamination reaction can take place, to give a carbenium ion species 2, which in turn can undergo a rearrangement and subsequent loss of a proton to yield a ring-enlarged cyclic ketone 3. This reaction is called the Tiffeneau-Demjanov reactionit is of wider scope than the original Demjanov reaction ... 

The starting material for the Tiffeneau-Demjanov reaction is available by various methods. A common route is the addition of nitromethane to a cyclic ketone—e.g. cyclopentanone 7—followed by a hydrogenation of the nitro group to give the /3-amino alcohol, e.g. 1 ... 

Various side-reactions may be observed with the Demjanov reaction the Tiffeneau-Demjanov reaction usually gives better yields of the ring-enlarged product. 

This reaction has been used to form ring-expanded cyclic ketones, a procedure known as the Tiffeneau-Demjanov reaction 1... 

Thiocarbonates, synthesis of, 17, 3 Thiocyanation of aromatic amines, phenols, and polynuclear hydrocarbons, 3, 6 Thiophenes, synthesis of, 6, 9 Thorpe-Ziegler condensation, 15, 1 31 Tiemann reaction, 3, 9 Tiffeneau-Demjanov reaction, 11, 2 Tin(n) enolates, 46, 1 Tin hydride method to prepare radicals,... 

Treatment of 4,4-dimethyl-2-phenyl-l,3-thiazole-5(4//)-thione with ethyl diazoacetate gives, among other products, ethyl 1,3-thiazine carboxylate (179) (99). The formation of 179 has been rationalized by an acid-catalyzed addition of ethyl diazoacetate to the thiocarbonyl ylide 177 to first give intermediate 178, which undergoes a subsequent ring enlargement reaction via a Tiffeneau-Demjanov rearrangement. 

The formation of diazonium salts from aromatic primary amines by reaction with nitrous acid undoubtedly involves the intermediate formation of V-nitroso compounds. The Demjanov and Tiffeneau-Demjanov ring expansions also involve V-nitroso compounds [2]. Some V-nitroso compounds have been used as sources of free radicals and as blowing agents. 

The stabilization of the intermediate as a carhenium - oxonium ion in the diazotization of P-amino alcohols (Tiffeneau-Demjanov rearrangement) is responsible for the formation of 4-bromo-5,5-dimethylbicyclo[2.1.1]hexane-l-carbaldehyde (30) in the reaction of l-amino-4-bromo-7,7-dimethylbicyclo[2.2.1]heptan-2-ol with nitric acid.96... 

But now commonly associated with Tiffeneau-Demianov rearrangement The classification now covers many reactions of the "pinacol type", including ... 

Bart Reaction Borsche (Cinnoline) Synthesis Demianov Rearranement Diazo Reaction Gattermann Reaction Gattermann Method Pschorr Arvlation Sandmever Reaction Schiemann Reaction (Bak-Schiemann JRxn) Tiffeneau-Demianov Reaction fVidman-Stoermer ([Pg.847]

The reaction of 2-chlorocyclohexanone with alkyl Grignard reagents -was first investigated by Tiffeneau and oo-workers1744-1748 in... 

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