name reaction b

Baeyer-Villiger Oxidation

The Baeyer-Villiger Oxidation is the oxidative cleavage of a carbon-carbon bond adjacent to a carbonyl, which converts ketones to esters and cyclic ketones to lactones. The Baeyer-Villiger can be carried out with peracids, such as MCBPA, or with hydrogen peroxide and a Lewis acid.

The regiospecificity of the reaction depends on the relative migratory ability of the substituents attached to the carbonyl. Substituents which are able to stabilize a positive charge migrate more readily, so that the order of preference is: tert. alkyl > cyclohexyl > sec. alkyl > phenyl > prim. alkyl > CH₃. In some cases, stereoelectronic or ring strain factors also affect the regiochemical outcome.

MECHANISM OF THE BAEYER-VILLIGER OXIDATION

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Baker-Venkataraman Rearrangement

The base-induced transfer of the ester acyl group in an o-acylated phenol ester, which leads to a 1,3-diketone. This reaction is related to theClaisen Condensation, and proceeds through the formation of an enolate, followed by intramolecular acyl transfer.

MECHANISM OF THE BAKER-VENKATARAMAN REARRANGEMENT

Balz-Schiemann Reaction

The conversion of aryl amines to aryl fluorides via diazotisation and subsequent thermal decomposition of the derived tetrafluoroborates or hexafluorophosphates. The decomposition may also be induced photochemically.

MECHANISM OF THE BALZ-SCHIEMANN REACTION

see Diazotisation.
The mechanism of the Balz-Schiemann reaction remains obscure. A possible pathway is shown below:

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Bamford-Stevens Reaction

Tosylhydrazones give alkenes upon treatment with strong bases. This reaction is performed in two steps, where the intermediate diazo compound may be isolated. Subsequent reaction with protic or aprotic solvents strongly influences the outcome of the reaction.
This reaction may be used to effect the overall transformation of a ketone to an alkene.
If an organolithium is used as the base, the reaction follows another mechanism without occurrence of carbenium ions and carbenes (see Shapiro Reaction).

MECHANISM OF THE BAMFORD-STEVENS REACTION

Carbenium ions are formed in protic solvents:

...and carbenes in aprotic solvents:

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Barton Decarboxylation

The radical decarboxylation of a Barton ester proceeds to the corresponding alkane after treatment with tributyltin hydride or t-butylmercaptan:

An alternative possibility is the introduction of a substituent by reaction with a suitable radical trapping agent:

MECHANISM OF THE BARTON DECARBOXYLATION

The initiation of the Barton Decarboxylation ( Bu₃Sn-H -> Bu₃Sn^. ) is effected with a radical initiator, and as with the Barton-McCombie Deoxygenation, the driving force for the reaction itself is the formation of the stable S-Sn bond.

In addition, Barton esters can also be cleaved photolytically or thermally:

If an excess of a suitable radical trapping agent is present in the reaction medium, substitution will occur; otherwise, radical recombination takes place to give the pyridyl sulfide: