Carbon leaving groups

Recently, the scope of the allylic substitution has been extended to sulfinate salts 84 to obtain allylic sulfones 85. Due to solubility problems of both nucleophile 84 and carbonate leaving group, a polar solvent mixture of DMF and 2-methoxyethanol had to be employed, which limits the reaction to the use of a phosphine ligand. Thus, various aryl sulfinates 84 and functionalized carbonates 81 could be converted to the corresponding allylic sulfones 85 with good to excellent yields and regioselectivites and complete retention of stereochemistry (eq. 2 in Scheme 20) [65]. 

Other workers have concluded that the transition state for the Menshutkin reaction is late with more nitrogen-alpha carbon bond formation than alpha carbon-leaving group bond rupture. For instance, Harris and coworkers51 found that the secondary alpha deuterium kinetic isotope effects (Table 8) decreased when a poorer nucleophile was used in the S v 2 reactions between 3,5-disubstituted pyridines and methyl iodide in 2-nitropropane at 25 °C (equation 38, Table 8). 

A variation of the general carbon leaving group scheme of Equation 5.26 is decarboxylation (Equations 5.27 and 5.28).139 In order for the fragmentation... 

Inversion of configuration requires that the nucleophile adds electrons to die a orbital of die carbon-tridate bond from die side opposite diat bond. As required by die stereochemistry, formation of die bond from azide to carbon is concurrent widi cleavage of the carbon leaving group bond. 

The reaction of benzyl methyl carbonate with sodium benzenesulflnate and different palladium catalysts has shown that the best yields were obtained when a Pd( 3-C3H5)Cl2 - (DPEphos) catalyst was used in DMSO at 80 °C.121 Most of the reactions gave >90% yields of the benzyl aryl sulfone. In the suggested mechanism, the methyl carbonate leaving group is displaced by the catalyst, forming an (j 3-benzyl)palladium intermediate that reacts with the sodium salt of the arenesulfinate. 

Figure 6.5 When a carbon-hydrogen bond is aligned trans-periplanar with a carbon-leaving group...

Figure 6.5, require alignment of a carbon-hydrogen bond with an adjacent carbon-leaving group bond. Furthermore, as shown in Figure 6.5, the relationship between these bonds is critical for elimination to occur. Specifically, the relevant bonds must adopt a trans relationship within the same plane. This relationship is referred to as frares-periplanar. 

Chiral sulfoxides are useful intermediates in asymmetric synthesis. A number of methods for their preparation were developed in the last decade. An interesting displacement of dimethylphosphonylmethyl moiety, a carbon leaving group, from sulfur by Grignard reagents was used to obtain enantiomerically purep-tolyl sulfoxides.3 4 Optically pure methyl 4-bromophenyl sulfinate was subjected to a one-pot sequence yielding unsymmetrical dialkyl sulfoxides in 60-97% yield and >98% ee. A simple one-pot synthesis of chiral sulfoxides from norephedrine-derived... 

The three types are not treated separately, but reactions are classified by leaving group. A. Carbon Leaving Groups... 

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