Amido selective

Potassium and sodium borohydride show greater selectivity in action than lithium aluminium hydride thus ketones or aldehydes may be reduced to alcohols whilst the cyano, nitro, amido and carbalkoxy groups remain unaffected. Furthermore, the reagent may be used in aqueous or aqueous-alcoholic solution. One simple application of its use will be described, viz., the reduction of m-nitrobenzaldehyde to m-nitrobenzyl alcohol ... 

The alkyl, amido, and alkoxy groups are activating and ortho-para-dkeciing, but not as strongly so as hydroxyl or amino groups. Synthetically useful conditions for selective substitution are available for essentially all the electrophiles in Scheme... 

The simplest method for obtaining selective fluonnation is to conduct reactions under conditions that invigorate the electrophilicity of fluorine In practice this method entails the creation of anionic or strongly nucleophilic reactive centers on substrate molecules while suppressing or reducing the tendency toward radical attack Numerous examples of seleetive fluorine attack on carbanionic, amido and carboxylato species are documented Especially abundant is alpha fluonnation of nitroalkanes in polar solvents [42 43, 44, 45 46] (equations 10-14)... 

Hexamethylenetetramine can serve as a source of ammonia in the reaction with a 2-(haloacet-amido)benzophenone. The intermediate salts 14, which can be isolated, are readily transformed into benzodiazepinones IS in refluxing ethanol (Method C). Selected examples are given.197 198... 

Closely related mixed amido/imido/guanidinato tantalum complexes of the type Ta(NR R )[(R R2N)C(NR )2]( = NR ) (R R = Me, Et R = Cy, Pr R = Pr", BuO were synthesized by the insertion of carbodiimides into to tantalum-amide bonds in imidotantalum triamide precursors, and the effects of ligand substitution on thermal properties were studied by TGA/DTA measurements. In addition, selected compounds were pyrolyzed at 600 °C and the decomposition products were studied by GC-MS and NMR spectroscopy. ... 

In addition to ester bonds with P (Section 10.2.1, Figures 10.1 and 10.2), some OPs have other ester bonds not involving P, which are readily broken by esteratic hydrolysis to bring about a loss of toxicity. Examples include the two carboxylester bonds of malathion, and the amido bond of dimethoate (Figure 10.2). The two carboxylester bonds of malathion can be cleaved by B-esterase attack, a conversion that provides the basis for the marked selectivity of this compound. Most insects lack an effective carboxylesterase, and for them malathion is highly toxic. Mammals and certain resistant insects, however, possess forms of carboxylesterase that rapidly hydrolyze these bonds, and are accordingly insensitive to malathion toxicity. 

New catalysts were prepared after optimisation of the Ugand structure. The most efficient organo catalyst for this reaction was an amido-thiourea derivative (Scheme 43). Interestingly, dissymmetrical ligands were more efficient and selective for this reaction. 

The sense of diastereoselectivity in the dynamic kinetic resolution of 2-substi-tuted / -keto esters depends on the structure of the keto ester. The ruthenium catalyst with atropisomeric diphosphine ligands (binap, MeO-biphep, synphos, etc.) induced syn-products in high diastereomeric and enantiomeric selectivity in the dynamic kinetic resolution of / -keto esters with an a-amido or carbamate moiety (Table 21.21) [119-121, 123, 125-127]. In contrast to the above examples of a-amido-/ -keto esters, the TsOH or HC1 salt of /l-keto esters with an a-amino unit were hydrogenated with excellent cwti-selectivity using ruthenium-atropiso-... 

Increasing interest is expressed in diastereoselective addition of organometallic reagents to the ON bond of chiral imines or their derivatives, as well as chiral catalyst-facilitated enantioselective addition of nucleophiles to pro-chiral imines.98 The imines frequently selected for investigation include N-masked imines such as oxime ethers, sulfenimines, and /V-trimcthylsilylimines (150-153). A variety of chiral modifiers, including chiral boron compounds, chiral diols, chiral hydroxy acids, A-sull onyl amino acids, and /V-sulfonyl amido alcohols 141-149, have been evaluated for their efficiency in enantioselective allylboration reactions.680... 

Delavirdine (4.91), a selective inhibitor of HIV-1 reverse transcriptase, also contains an amido N-atom as part of a piperazine ring. In rats and monkeys, cleavage of the amide bond constituted only a minor pathway [56]. 

Bromocyclopentitols and amino(or amido)bromocyclopentitols having a C—Br bond trans to two vicinal hydroxy groups show selectivity in base-promoted epoxide formation, e.g. (52) gives (53) by path a, rather than (54) by path... 

An additional means of performing a selective cross-benzoin was reported in 2001 when Mnrry and co-workers expanded benzoin methodology to include trapping of acyl imines XIX formed in situ (Scheme 6) [53], The authors chose to use a-amido sulfones due to their stability and the relative ease of acyl imine liberation. The parent reaction combines pyridine 4-carboxaldehyde 51 and tosylamide 52 in 98% yield in the presence of pre-catalyst 54 and triethylamine (Scheme 6). 

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