Reagents synthesis

It is noteworthy that reaction diastereoselectivity closely parallels the isomeric purity of the allyiboronates, thus underscoring the requirement that the method of reagent synthesis be highly stereoselective. The data presented in Table 1 also provide strong evidence for the involvement of chair-like, cyclic transition states, analogous to the transition states previously invoked for aldol reactions46. 

Grignard reaction, addition of methyl-magnesium bromide to thiophos-phoryl chloride, 45,102 Grignard reagents, synthesis and utility of unsolvated, 47, 116 titration of, 48, 48... 

P Li, J-C Xu. New and highly efficient immonium type peptide coupling reagents synthesis, mechanism and application. Tetrahedron 56, 4437, 2000. 

The assembly consists of three fritted jacketed columns (each 2 cm wide) including two top columns (type A) for reagent synthesis a catalytic column (type B) into which the reagent columns feed and a scavenger resin column (type C) below the catalytic column. (Adapted from Hafez et ah, 2001)... 

The assembly consists of three fritted jacketed columns (each 2 cm wide), including two top columns (type A) for reagent synthesis, a catalytic column... 

Reaction with ambient reagent Synthesis of heterocyclic compounds Nu-... 

The ability to provide highly functionalized reagents, such as unsaturated silanes and vinyl boronates, starting from terminal olefins is one of the most attractive attributes of CM, particularly when traditional methods for the preparation of such compounds are not synthetically straightforward. Therefore, significant research has been undertaken to determine the broad-spectrum chemoselectivity of olefin metathesis catalysts. In many cases, the use of a CM protocol in reagent synthesis is completely orthogonal to alternative methods of preparation. 

Allyl- and vinylsilane chemistry was one of the first areas of reagent synthesis impacted by CM methodology. Allylsilanes are commonly employed in nucleophilic additions to carbonyl compounds, epoxides, and Michael acceptors (the Sakurai reaction) vinylsilanes are useful reagents for palladium-coupling reactions. As the ubiquitous application of CM to this substrate class has recently been described in several excellent reviews, this topic will not be discussed in detail, with the exception of the use of silane moieties to direct CM stereoselectivity (previously discussed in Section 11.06.3.2). 

One of the most unique applications of CM to reagent synthesis is described in a report by Zhang and Herndon, where catalysts 2 and 5 were used to effect the homologation of homoallylic Fischer carbene complexes (Equation (4)). The E/Z ratios observed in these reactions using catalyst 5 were typically 9 1. Highly reactive, electron-neutral olefins were... 

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