Product regioselectivity

INTERPRETING THE OBSERVED SUBSTRATE SELECTIVITY AND THE PRODUCT REGIOSELECTIVITY IN ORF2-CATALYZED PRENYLATION FROM X-RAY STRUCTURES... 

In the next section, we will demonstrate how the QM/MM refinement strategy was combined with advanced sampling techniques to resolve the ambiguous electron densities of a substrate complexed with Orf2, an aromatic prenyltransferase, and successfully clarify the relaxed substrate specificity and product regioselectivity. 

On the other hand, platinum-catalyzed silaboration of allenes results in an opposite regiochemical preference. Silaboration of a 1,1-disubstituted allene affords terminal addition product regioselectively in the presence of a platinum catalyst, whereas the internal addition product is obtained with a Pd2(dba)3-PPh3 catalyst (Scheme 49).227... 

Paine MJ, McLaughlin LA, Flanagan JU, et al. Residues glutamate 216 and aspartate 301 are key determinants of substrate specificity and product regioselectivity in cytochrome P450 2D6. J Biol Chem 2003 278(6) 4021-4027. 

Isolated yield after column chromatgraphy. Determined by NMR of the crude product. Regioselectivity was determined as i/n > 98/2. 

When it is desired to use an unsymmetrical ketone as the active-hydrogen component, it is possible to get two products. Regioselectivity has been obtained by treatment of the... 

Azido-phenylselenenylations of olefinic compounds can be effected with BAIB/PhSeSePh/NaN3 in CH2C12 (Scheme 14) [37]. Such additions proceed in anti-Markovnikov fashion and appear to be initiated by addition of the azido radical to the C,C-double bond. While cyclohexene and ds-4-octene gave 3 1 and 2 1 mixtures of diastereomeric adducts under these conditions, dihydropy-ran was converted cleanly to the trans-addition product. Regioselective azido-phenylselenenylations of dihydropyran derivatives and O-protected glycals with this reagent have also been documented [21,38,39]. 

Sequential one-pot synthesis Reactions occur sequentially Variable reaction conditions (e.g., pH, T°C) No isolation of intermediate products Regioselective enzymatic protection and chemical acetylation 15... 

Triorganogallium and -indium reagents react with a,/3-unsaturated nitrile, ketone, and ester to give 1,4-addition products regioselectively (Table 31). In contrast, the reaction of allylgallium and allylindium sesquihalides with a,/3-unsaturated carbonyl compounds proceed in a 1,2-addition mode, whereas 1,4-addition takes place with a,/3-unsaturated nitriles.294... 

HRh(CO)4 is used by Ruhrchemie in the hydroformylation of certain branched alkenes that can only give a single product due to the location of the branch that restricts both alkene isomerization and product regioselectivity. In this special case, the high activity of HRh(CO)4 is not off-set by poor aldehyde regioselectivity. 

Unsaturated lactones lacking substitution at C-4 are the simi est ones available via this general type of cycloaddition. Several syntheses of these lactones are of practical value, including two Pd-based meth-ods. However, the considerable utility of metal carbonyl anions in lactone synthesis is illustrated by a rhodium carbonyl anion catalyst system which gives very high yields upon reaction with a variety of internal alkynes under weakly basic aqueous conditions, essentially water-gas shift conditions. These conditions were established to maximize chemoselectivity with respect to other possible alkyne carbonylation products. Regioselectivity is modest in this process, but was not examined systematic ly (equation 13). ... 

With substituted unsymmetrical benzene-1,2-diamines and unsymmetrical reagents this type of reaction leads to isomeric products. Regioselective synthesis of quinoxaline derivatives and the effect of substituents at C3 in the aromatic ring on annulation has been studied for unsymmetrically substituted starting benzene-1,2-diamine derivatives. ... 

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