Acyl halides with active hydrogen

Enol Ethers and Esters 0-15 O-Alkylation of carbonyl compounds with diazo alkanes 0-17 Transetherification 0-20 Reaction between acyl halides and active hydrogen compounds 0-23 Transesterification 0-24 Acylation of vinylic halides 0-94 Alkylation with ortho esters 0-107 O-Acylation of 1,3-dicarbonyl compounds... 

The key compounds in the synthesis of 4,4 -dithiocello- and -xylotrioses are the per-acetylated 1,4-dithiodisaccharides (43 a, 43 b) (Scheme 14) which are obtained from acylated (39 a, 39 b) by hydrogen bromide treatment and displacement of the halide by potassium or tetrabutylammonium thioacetate. Total deacetylation of the donors and reaction with triflated acceptors (34 a) or (34b) afforded the expected trisaccharides which can be converted after conventional treatment, into free trisaccharides (44d,44e,44g and 44 h) [40]. Using the same stepwise procedure, but with activation of the donor by selective in situ S-de-acetylation and activation, the cellotetraoside (44 i) and cellopentaoside (44j) were obtained in good yield [41]. 

The active hydrogens of pseudoureas react with various reagents, such as sodium hypochlorite [72], acyl halides [73], sulfonyl halides [19], isocyanates [26], isothiocyanates [26, 74] cyanamide, [75] and esters [76], to give linear or cyclic derivatives as shown in Scheme 2. 

Ishihara, K. Kubota, M. Yamamoto, H. First application of hydrogen bonding interactions to the design of asymmetric acylation of meso-diols with optically active acyl halides. Synlett 1994, 611-614. 

The bisacylation of methylene-active compounds mentioned above can be avoided by using acylimidazoles in place of acyl halides (acylimidazoles are obtained from the carboxylic acid and sulfinyldiimidazole) for example, reaction of the magnesium enolate of ethyl hydrogen malonate and an acylimid-azole, with concomitant decarboxylation, gives the corresponding / -oxo ester 430... 

Rh(TTP) reacts with alkyl halides, acyl halides, aroyl halides, and sulfonyl halides, but it shows no evidence of reaction with molecular hydrogen. These observations further emphasize the fact that Rh(TTP) is essentially a nucleophile and it therefore reacts with those reagents RX that can oxidatively add by nucleophilic attack (34). Rh(TTP) does not react with H2, and H2 seems always to add to (P complexes via a concerted mechanism (35). It appears that Rh(TTP) has very little diradical character, i.e. it is not a good analog of a carbene (35). It is possible that this unreactivity may be associated with the stereochemistry of chelation by the macrocyclic ligand. Earlier studies on the oxidative addition reactions of Rh(I) complex with a tetraaza macrocycle revealed that the Rh(I) had strong nucleophilic properties but the activation of molecular H2 was not reported (36, 37). This possibility is supported by reports that dialkyl sulfide complexes of rhodium chloride catalyze the hydrogenation of olefins (38). 

Transition-metal acetylides react readily with metal carbonyls to form derivatives. Thus (7t-Cp)2Ti(C CPh)2 and Ni(CO)4 afford (22). The oxidative additions of alkyl and acyl halides, RCOCl (R = Me or Ph), to [(7i-Cp)2Ti(CO)2] yield the corresponding [(7i-Cp)2Ti(Cl)C(0)R] compounds, and 9,10-phenanthraquinone affords (23). [(7i-Cp)2TiPh2] and [(7t-Cp)2 Ti(Me)Cl] have been shown to be active hydrogenation catalysts and the n.m.r. spectra of several [(7t-Cp)2TiR2] and [(7i-Cp)2Ti(R)Cl] compounds have been re-investigated and previous interpretations of such data questioned. ... 

To present, silica-supported rhodium catalysts have been successfully used for hydrogenation, hydroformylation, and hydrosilylation reactions. Zhang and coworkers" developed a heterogeneous rhodium complexes 23 catalyzed carbon-heteroatom bond formation. The reaction couples disulfides 21 or diselenides with an alkyl or acyl halide to generate unsymmetrical sulfides (24) and selenides in good yields. The catalyst could be easily recovered and recycled by filtration of the reaction solution and re-used for five cycles without significant loss of activity (maintains over 90% yield)." ... 

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