Catalysis of isomerization

Catalysis of isomerization of amides, derivatives of cyclic amines 00ACR849. 

The thione thiol rearrangement of 0-alkyl phosphinothioic esters is catalysed by acids. In an investigation of the catalysis of isomerization of the esters Me2P(S)OPr and Ph2P(S)OMe by trifluoroacetic acid by means of P NMR spectroscopy, Bruzik and Stec assigned transient signals to the species 112. ... 

This situation contrasts with rhodium(i) catalysis of isomerization, where only one carbon-carbon bond is thought to be broken, and indeed comparisons of bicyclobutane isomerizations catalysed by silver(i) perchlorate and by bis-benzonitrilepalladium(n) dichloride, and of silver(i)-catalysed isomerizations of bicyclobutanes and of tricycloheptane, are claimed to indicate that only one carbon-carbon bond is broken in forming the argentocarbonium ion intermediate (20). However, it is admitted that... 

Some recently reported examples of homogeneous catalysis of isomerization of alkenes by transition-metal complexes are listed in Table... 

In contrast to triphenylphosphine-modified rhodium catalysis, a high aldehyde product isomer ratio via cobalt-catalyzed hydroformylation requires high CO partial pressures, eg, 9 MPa (1305 psi) and 110°C. Under such conditions alkyl isomerization is almost completely suppressed, and the 4.4 1 isomer ratio reflects the precursor mixture which contains principally the kinetically favored -butyryl to isobutyryl cobalt tetracarbonyl. At lower CO partial pressures, eg, 0.25 MPa (36.25 psi) and 110°C, the rate of isomerization of the -butyryl cobalt intermediate is competitive with butyryl reductive elimination to aldehyde. The product n/iso ratio of 1.6 1 obtained under these conditions reflects the equihbrium isomer ratio of the precursor butyryl cobalt tetracarbonyls (11). 

The three cycles have to turn over in the same range of temperature. This catalytic approach of the DeNOx reaction is not new. There is the same process for isomerization of alkanes, where there are also 3 catalytic cycles which have to turn over simultaneously (bifunctional catalysis). The kinetics of isomerization is given by only one cycle, the other two turning over very rapidly and are near equilibrium [13]. 

Synthesis of isomeric chiral protected (63 )-6-amino-hexahydro-2,7-dioxopyrazolo[l,2- ]pyrazole-l-carboxylic acid 280 is shown in Scheme 36. Crude vinyl phosphonate 275, obtained by treatment of diethyl allyloxycarbonylmethyl-phosphonate with acetic anhydride and tetramethyl diaminomethane as a formaldehyde equivalent, was used in the Michael addition to chiral 4-(f-butoxycarbonylamino)pyrazolidin-3-one 272. The Michael addition is run in dichloro-methane followed by addition of f-butyl oxalyl chloride and 2 equiv of Huning s base in the same pot to provide 276 in 58% yield. The allyl ester is deprotected using palladium catalysis to give the corresponding acid 277, which is... 

Partitioning of carbocations between addition of nucleophiles and deprotonation, 35, 67 Perchloro-organic chemistry structure, spectroscopy and reaction pathways, 25, 267 Permutational isomerization of pentavalent phosphorus compounds, 9, 25 Phase-transfer catalysis by quaternary ammonium salts, 15, 267 Phosphate esters, mechanism and catalysis of nucleophilic substitution in, 25, 99 Phosphorus compounds, pentavalent, turnstile rearrangement and pseudoration in permutational isomerization, 9, 25... 

An olefin metathesis/double bond isomerization sequence can be promoted by the catalysis of in situ generated ruthenium hydride species from ruthenium complex 1 (Scheme 41 ).68... 

A related cyclization of 2-(alkynyl)phenylisocyanates with terminal alkynes to oxindoles was also reported by the same group (Equation (115)).472 (E)-exo-olefinic oxoindoles are selectively obtained. It was proposed that a palladium acetylide generated by the C-H activation of terminal alkynes regioselectively inserts to the alkyne moiety and the resulting vinylpalladium intermediate adds to the C=0 part of the isocyanate to give a (Z)-oxindole. This (Z)-isomer is isomerized to the ( )-isomer under the reaction conditions through catalysis of the phosphine. 

The isomerization of an O-silyl ketene acetal to a C-silyl ester is catalyzed by a cationic zirconocene—alkoxide complex [92], This catalysis was observed as a side reaction in the zirconocene-catalyzed Mukaiyama aldol reactions and has not yet found synthetic use. The solvent-free bis(triflate) [Cp2Zr(OTf)2] also catalyzes the reaction in nitromethane (no reaction in dichloromethane), but in this case there may be competitive catalysis by TMSOTf (cf. the above discussion of the catalysis of the Mukaiyama aldol reaction) [91] (Scheme 8.51). 

Under catalysis of Ag+, 2,3-allenylamines can undergo cycloisomerization to afford N-containing heterocycles [135,136]. Such metal-mediated isomerizations are discussed in detail in Chapter 15. 

Scheme 25). l-Oxo-2,8-diphenyl-2,5,8 triaza-1 X -phosphabicyclo[3.3.0]octane (68) formed by acid catalysis of the bicyclic phosphoric triamide (67) has been found to isomerize via a new type of rearrangement to yield the ring contracted 3-[2-(phenylamino)ethyl]-2-oxo-2-ethoxy-l-phenyl-l,3,2 A, -diazaphospholidine (69). The rearrangement has been explained in terms of intramolecular 1,5-nucleophilic attack... 

Catalyses of HY and HL are not controlled by sterlc circumstances of pore and channel. HY and HL have enough spaces for transition state to allow the formation of all IPBP Isomers. Product distribution changes markedly by increasing reaction temperature. Catalysis at low temperatures is determined by the reactivity of each position of biphenyl molecule to yield 2- and 4-IPBP as principal isomers. However, the selectivity of 3-IPBP increases extensively with decrease of 2-IPBP with rising temperature, and an equimolar mixture of 3-and 4-IPBP is produced at high temperatures. These changes in product distribution are ascribed to the isomerization of 2-IPBP to the more stable 3-IPBP by a de-alkylatlon and alkylation mechanism. Catalysis of HZSM-5 at 300°C is nonselective with low activity. The reaction occurs at external surface because the pore is too small to allow the entrance of biphenyl molecule. 

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