Alkyl formates, azodicarboxylate

The system of PhsP-diethyl azodicarboxylate-hydroxy compound-LiBr allows the formation of alkyl bromides under mild conditions (equation An 5N2-type displacement of an intermediate alkoxy-... 

This reaction was first reported by Mitsunobu in 1967. It is the alkylation of compounds with active protons by using primary or secondary alcohols as the alkylating agents in combination with triphenylphosphine and diethyl azodicarboxylate (DEAD) or diisopropyl azodicarboxylate (DIAD), to form molecules like esters, ethers, thioethers, and amines. Therefore, this reaction is generally known as the Mitsunobu reaction or Mitsunobu coupling. In addition, the specific reaction for forming esters by means of DEAD (or DIAD) and PPhs is generally referred to as the Mitsunobu esterification." Occasionally, the Mitsunobu reaction is also called the Mitsunobu transformation (for the conversion of alcohol into amines) or Mitsunobu cyclizafion (for the formation of cyclic compounds). Because of its intrinsic features of stereospecificity, as well as its occurrence in neutral media and at room temperature without a prerequisite activation of alcohol, this reaction has been extensively studied and used to synthesize a variety of compounds since 1970. 

Dealkylation of Amines. Treatment of a secondary or tertiary amine with diethyl azodicarboxylate in nonpolar solvents followed by acidic hydrolysis leads to the formation of mon-odealkylated amines. The mechanism of this reaction is believed to involve the formation of a triaza adduct (by Michael addition) followed by a two-step ylide rearrangement yielding an alkyl-substituted hydrazocarboxylate. Research on unsymmetrically substituted amines suggests that benzyl groups are more easily removed than alkyl groups methyl groups are the hardest to remove except in cyclic amines like iV-methylpiperidine (eq 3). The Al-dealkylation of imines has also been reported. ... 

Tosylate Formation with Inversion of Configuration. Alkyl tosylates can be formed directly from secondary alcohol functionality with retention of carbon stereochemistry by treatment withp-Toluenesulfonyl Chloride and Pyridine. However, conversion of an alcohol to the corresponding tosylate of opposite stereochemistry typically requires a minimum of three steps. For example, inversion of the stereocenter with benzoic acid under Mitsunobu reaction conditions, hydrolysis of the resulting ester, and finally conventional tosylation of the alcohol, provides an attractive route for this transformation. A similar route, the inversion of a secondary alcohol directly with p-TsOH, Diethyl Azodicarboxylate (DEAD), and Triphenylphosphine, does not produce the desired tosylate product. ... 

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