Neighboring participation

Intramolecular nucleophilic displacements, such as those in lactone formation, have faster reaction rates than intermolecular S,42 reactions because the latter require two species to collide. The neighboring participant is said to furnish anchimeric assistance. 

Scheme 7 shows examples of 1,2 trans-glycosides synthesized from MOP glycosyl donors that have neighboring participating groups. In the presence of Cu(OTf)2, the... 

Katagiri, N. et al. A Highly Efficient Synthesis of the Antiviral Agent (+)-Cyclaradine Involving the Regioselective Cleavage of Epoxide by Neighboring Participation. 2.4 1997 [136]... 

Narasaka, K, Ichikawa, Y I, Kubota, H, Stereoselective preparation of p-C-glycosides from 2-deoxyribose utilizing neighboring participation by 3-O-methylsulfinylethyl group, Chem. Lett., 2139-2142, 1987. 

The use of neighboring participating groups permits the formation of 1,2-trans glycosides (e. g. 326, O Scheme 53). The choice of solvent and, to some extent, the choice of activator, was used to control the alp ratio in glycosyl donors without participating groups at 02. TMSOTf-... 

According to strategy 1, OSW-1 (1) was broken down into steroid 2 and di-sasccharide donor 3 (Scheme 3). Glycosyl trichloroacetimidate with a neighboring participation group (3) is believed to be one of the most reliable donors [8b]. Since... 

PROBLEM 21.35 When Z = OCH3, about 93% of the products of solvolysis of 1 can be attributed to neighboring phenyl group participation. When Z = NO2, essentially none of the products come from neighboring participation by phenyl. Eixplain. 

An interesting intramolecular nucleophilic displacement is the first-order neighboring participation of the NMe2 group during the hydrolysis of 4-substituted phenyl esters of y-(iV,iV -dimethylamino)butyric and valeric acids (reaction 15) The rate constant for the formation... 

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