Reaction catalytic transfer hydrogenation

HCO2NH4, have been used for catalytic transfer hydrogenation, which is in general a more rapid reaction than catalytic hydrogenation. 

In the sixth chapter the activation of O-H bonds of water, alcohols and carboxylic acids, and their addition to multiple bonds is reported. Since the formally oxidative addition of ROH gives rise to hydrido(hydroxo) complexes, [MH(OR)Ln] which are postulated as intermediates in many important reactions (water gas shift reaction, Wacker-chemistry, catalytic transfer hydrogenations etc.) the authors of this chapter,... 

The concept of performing microwave synthesis in room temperature ionic liquids (RTIL) as reaction media has been applied to several different organic transformations (Scheme 4.18), such as 1,3-dipolar cycloaddition reactions [54], catalytic transfer hydrogenations [55], ring-closing metathesis [56], the conversion of alcohols to alkyl halides [57, 58], and several others [59-61],... 

In MW-assisted chemistry reduction reactions were the last to appear on the scene the use of ammonium formate and catalytic transfer hydrogenation were initial examples [23 b]. 

The rapid microwave-assisted deprotection of N-benzyl carbamate (Cbz) and AT-benzyl (Bn) derivatives in solution as well as on solid support was reported by Daga et al.26 Within this report, amino groups protected as benzyl carbamates or with simple benzyl groups could be deprotected in a few minutes by microwave-assisted catalytic transfer hydrogenation with palladium charcoal in isopropanol, employing ammonium formate as the hydrogen donor (Scheme 7.6). Both MeO-PEG and PS Wang-resin were used as soluble and solid supports, respectively, in these reactions. 

An intramolecular [3 + 2] dipolar cycloaddition reaction has also been exploited in the design of a concise, stereospecific synthesis of ( )-a-lycorane (57) (119). Thus, cyclization of the azomethine ylide 145, which was produced in situ by the reaction of 144 with IV-benzylglycine, in refluxing toluene furnished the cw-hydroindole 146 as the exclusive product (Scheme 14). The transformation of 146 to racemic a-lycorane (57) was then achieved by N-debenzylation via catalytic, transfer hydrogenation and subsequent Pictet-Spengler cyclization. 

In a very recent computational study, Diggle et al. have calculated the activation barriers for C(aryl)-X activation (X = H, F, OH, NH, CH3) as 0 (H), 9 (F), 12 (OH), 20 (NH ) and 21.3 kcal mol (CH3), respectively [155]. In comparison, the activation barrier for C(sp3)-H is 6.6 kcal moF [156]. C-X activation occurs under reaction conditions relevant for homogenous catalysis [157], but does not always result in decomposition as C-H activation is often reversible and can be exploited in catalytic transfer hydrogenations involving alcohols [156]. 

It is also worthwhile to note that the relatively slow catalytic hydrogenolysis of A/ -Z-protected peptide derivatives pemnits some interesting chemical transformations to be performed in situ. For example, direct conversion of Z protection to Boc protection is possible when the hydrogenation is conducted in the presence of di-tert-butyl dicarbonate under neutral conditions.h Alternatively, the same transformation is achieved by the use of triethylsilane and di-tert-butyl dicarbonate in ethanol with catalytic amounts of palladium(II) acetate.h 1 More efficiently this one-pot transformation is achieved by catalytic transfer hydrogenation in the presence of di-terf-butyl dicarbonate (cf. Section 2.1.1.1.3.1.1.6).h l Similarly, peptide cyclization reactions have been performed in situ over Pd/C and the high yields of cyclic monomers are attributed to the high dilution effect as well as to catalysis of the charcoal surface.h l... 

Homogeneous catalytic transfer-hydrogenation. Sasson and Blum1 introduced the use of this metal catalyst for transfer of hydrogen from primary alcohols to a,/J-unsaturated carbonyl compounds. Thus when benzyl alcohol is heated under nitrogen at 200° for 2 hr. with benzalacetone and the catalyst, benzaldehyde (90% yield) and 4-phenylbutane-2-one (92 % yield) are formed. The reaction can be carried out in a... 

Also, dialysis was reported to remove TMCs from reaction mixtures. No mechanical pressure is needed here, clearly facilitating the mechanical and safety requirements. The first proof of concept was given with Ru-BINAP confined in a PDMS- envelop simply submerged in the reactor. In a catalytic transfer hydrogenation, the PDMS-membrane retained the catalyst... 

Propanol is a useful hydrogen donor for catalytic transfer hydrogenation of ketones. However, the unfavorable ketone alcohol equilibrium ratio often prevents a high conversion [121]. Moreover, the occurrence of its reverse process, due to the 2-propanol/alcoholic product and substrate/acetone structural similarities, frequently deteriorates the enantiomeric purity of the chiral product at the late stage of reaction. Use of the formic acid, another well-behaving and in-... 

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