And neighboring-group participation

Cyclization of hydrazone 38 with mercuric oxide and EDTA gave dihy-drotriazine 39 (87AP198). On the other hand, methyl hydrazone 38, under 4-electron withdrawal and neighboring group participation reacts with the same reagent to give lactam 40, a useful precursor for the synthesis of the pyrrolo[2,l-c]triazinium salt 41 by cyclization with perchloric acid (87AP258) (Scheme 12). 

The Mitsunobu reaction proved to be useful for the synthesis of aryl alkyl ethers from alcohols and phenols. The method proceeds under mild conditions and tolerates many functional groups with inversion of configuration, as exemplified by the reactions of lactate and ewrfo-5-norbornen-2-ol (equations 4 and Neighboring group participation,... 

Competing hydrolysis via attack of H2O on the carbocation kc) and concerted attack of water on the diazonium ion (A s) result in partial inversion of configuration, if steric hindrance and neighboring group participation can be neglected (e.g., for 7.50). 

CHAPTER 21 Intramolecular Reactions and Neighboring Group Participation... 

It is frequently found that at least four processes can occur in y-haloamines, that is fragmentation, nucleophilic displacement, 1,2-elimination and neighboring-group participation . Their relative importance is determined mainly by structure, stereochemistry... 

Reaction with Phenols and Other Oxygen Nucleophiles. When alcohols react with phenols, DEAD, and TPP, the corresponding aryl alkyl ethers are produced. A tertiary amine may facilitate the reaction. In general, the reaction proceeds with clean inversion of chiral secondary carbinol centers (eq 2 AH = a phenol). Depending on the structure of the substrate, al-lylic rearrangement and neighboring group participation can... 

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