Benzyl 2-pyridyl carbonate

Benzyl chloroformate (Z-Cl) is employed to prepare benzyl 2-pyridyl carbonate 854 from 2-hydroxypyridine 724 in 89% yield [625]. Benzyl 2-pyridyl carbonate is a reagent for introducing the Z-residue on amino functions of amino acids. 

Mixed alkyl carbonates, such as benzyl 2-pyridyl carbonate 854 and t-butyl 2-pyridyl carbonate 878, are useful reagents for introducing Z or Boc residues as protective groups due to the fact that 2-pyridinol is an excellent leaving group [625, 638). 

Aminolysis of benzyl 4-pyridyl carbonate (14 R = PhCH2) by a series of alicyclic secondary amines in MeCN and in water proceeded via a stepwise mechanism. This is in contrast to a similar previously reported aminolysis of benzyl 2-pyridyl carbonate (15 R = PhCH2) that proceeded via a forced concerted mechanism because of the... 

The Sg2 reaction on the 5p -like hybridized carbanion tends to proceed with inversion of the stereochemistry [45]. It is reasonable that a-thio carbanions, having higher s character than a-oxy carbanions, more frequently invert the stereochemistry on the anionic carbon in the reaction with electrophiles. As in the case of a-lithiated benzyl 2-pyridyl sulfide, the reaction of a-lithiated benzyl 2-quinolyl sulfide also proceeds through a dynamic thermodynamic resolution pathway. The quinolyl group is an excellent protecting group of thiols [46] and can be removed to yield the corresponding chiral thiols without racemization (Tables) [47]. 

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