Methylation addition

Hydrobis(ethoxycarbonyl)methyl Addition - Michael Addition... 

Feringa and co-workers found that Cu(OTf)2-29 can catalyze the addition of Me2Al to lactam to give corresponding methyl addition product with moderate enantioselectivity (68% ee Scheme 45).75... 

Figure 8.20 (a) The synthesis of phosphocreatine. The compound guanidinoacetate is formed from arginine and glycine in the kidney and is then transported to the liver where it is methylated addition of CHj (see Chapter 15) to form creatine (see Appendix 8.4 for details). Creatine is taken up by tissues/ organs/cells and phosphorylated to form phosphocreatine, particularly in muscle, (b) Conversion of phosphocreatine and creatine to creatinine in muscle. Creatinine is gradually formed and then released into blood and excreted in urine. 

A comparison of the stereochemistry of the 2-vinyl pyridine addition to [2a] with that of methylation addition is particularly instructive. Table 2 shows the stereochemistry of formation of [7a] as a function of counterion size and coordination. 

An unusual step in a synthesis of (+)-muscopyridine [146] is the methyl addition on an enolate. It appears that the oxygenated carbon still retains sufficient acceptor character by virtue of its relationship to the pyridine nitrogen (cf. reactivity of 2-vinyl-pyridine). 

MEOS microsomal ethanol oxidizing system, mercapto- — SH group, metallothionein metal-binding protein, methylation addition of a methyl group. 

Stereoselective methyl addition occurs from the convex face (the 3°-amide is inert to the cuprate reagent). 

Rhodium Y zeolites appear to be efficient at significantly lower temperature than rhodium X zeolites. This might be due to the higher polarization ability of the Y type zeolite which would favor the methyl addition onto the rhodium dicarbonyl which is the slow step in the case of rhodium. 

Methyl substitntion at the termini of 38, giving (3Z)-3-heptene-l,5-diyne 48 and (4Z) -octene-2,6-diyne 49, only slightly increases the cd distance, yet the activation barrier increases by 3-4 kcal mol" with each methyl addition (Table 4.11). 

Reaction of Ruthenium Carbonyls with Alkyl Radicals Boese and Goldman reported that in the presence of aryl ketones, d8 metal carbonyls such as Ru(CO)3(dmpe) mediate photocatalytic carbonylation of alkanes via a free radical mechanism.161 The activity was proposed to be initiated by the addition of an alkyl radical to the metal carbonyl and the formation of a metal-acyl radical intermediate. The transition states and the products of the reaction between alkyl radicals and ruthenium carbonyls were studied utilizing the B3LYP level of theory.162 The methyl addition to a carbonyl of Ru(CO)5 or Ru(CO)3(dmpe) was computed to be about 6 kcal/mol more exothermic than addition to free CO. 

FIGURE 10.20 Selected structural parameters, in degrees and A, of the transition states and products of methyl addition to 1 and their electronic energy ( b3lyp) relative to the separate reactants.162 Reproduced with permission from reference 162. Copyright 2008, American Chemical Society. 

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