Allylic amide isomerization

Allylic amide isomerization, 117 Allylic amine isomerization ab initio calculations, 110 catalytic cycle, 104 cobalt-catalyzed, 98 double-bond migration, 104 isotope-labeling experiments, 103 kinetics, 103 mechanism, 103 model system, 110 NMR study, 104 rhodium-catalyzed, 9, 98 Allylnickel halides, 170 Allylpalladium intermediates, 193 Allylsilane protodesilylation, 305 Aluminum, chiral catalysts, 216, 234, 310 Amide dimers, NMR spectra, 282, 284 Amines ... 

Metathesis of N-tosylated ene-amides and yne-amides has been less extensively investigated. An example of the RCM of ene-amides is a new indole synthesis developed by Nishida [79] metathesis precursor 96 (prepared by ruthenium-catalyzed isomerization of the corresponding allyl amide) is cy-clized to indole 97 in the presence of 56d (Eq. 13). 

In the presence of a cationic Rh[((/ )-binap)(cod)] complex, geranyl or neryl amides isomerize slowly to give a mixture of the corresponding enamide and dienamide (Scheme 20) (2). The optical purity of the chiral enamide is high, but the chemical yield is low. Certain cyclic allylic amides give the enamide isomers in a high ee. With a DIOP-Rh catalyst, prochiral allylic alcohols are converted to optically active aldehydes with low ee (31). 

Isomerization of N-allyl amide to N-propenyl amide is a key step of the deprotection of an amino group. ( )-N-Aryl-N-(l-propenyl)ethanamides 35 are obtained via the double bond migration of N-aryl-N-allylamide 34 catalyzed by a ruthenium hydride complex [19]. The configuration of the N-propenyl moiety in the product is almost E, and the high E selectivity is probably due to the steric repulsion between the aryl group and the methyl substituent of the propenyl group (Eq. 12.13). 

It is well known that silylation of allyl derivatives with vinylsilane catalyzed by a ruthenium hydride complex is accompanied by isomerization ofpropen-l-yl to propen-2-yl derivatives as well as homo-coupling of vinylsilane when equimolar amounts of the initial substances are used. If catalyst I was used in the SC of allyl amide and allyl amine with vinylsilanes, a S-fold excess of olefin to vinylsilane was used to stop homocoupling of vinylsilane, but simultaneously no more than 5% of isomerization of allyl compound was observed [19, 26]. When allyl boronate is used instead of allylamine under mild conditions (20 - 40 °C), the two reactions catalyzed by I and IV yield stereoselectively -product (see Scheme 4) [26]. 

Pyridine, 2-methylpyridine, and 2,4,6-collidinehave been added to avoid acidic conditions (to prevent secondary isomerizations) without deactivation of the silver salt by complexation or precipitation. In the absence of a nucleophile, pyridine forms allylic pyridinium salts and acetonitrile forms allylic amides. For example, formation of 5 and 6. ... 

KHMDS" and LDA also cause isomerization of allyl amides. 

As a further application of the reaction, the conversion of an endocyclic double bond to an c.xo-methylene is possible[382]. The epoxidation of an cWo-alkene followed by diethylaluminum amide-mediated isomerization affords the allylic alcohol 583 with an exo double bond[383]. The hydroxy group is eliminated selectively by Pd-catalyzed hydrogenolysis after converting it into allylic formate, yielding the c.ro-methylene compound 584. The conversion of carvone (585) into l,3-disiloxy-4-methylenecyclohexane (586) is an example[382]. 

The commonest of these for oxirane opening are amines and azide ion [amide ions promote isomerization to allylic alcohols (Section 5.05.3.2.2)]. Reaction with azide can be used in a sequence for converting oxiranes into aziridines (Scheme 49) and this has been employed in the synthesis of the heteroannulenes (57) and (58) (80CB3127, 79AG(E)962). 

Allylmagnesium bromide, 41, 49 reaction with acrolein, 41, 49 5-Allyl-l,2,3,4,5-pentachlorocyclopen-tadiene, 43, 92 Allyltriphenyltin, 41, 31 reaction with phenyllithium, 41, 30 Aluminum chloride, as catalyst, for isomerization, 42, 9 for nuclear bromination and chlorination of aromatic aldehydes and ketones, 40, 9 as Friedel-Crafts catalyst, 41, 1 Amidation, of aniline with maleic anhydride, 41, 93... 

Allyl groups attached directly to amine or amide nitrogen can be removed by isomerization and hydrolysis.228 These reactions are analogous to those used to cleave allylic ethers (see p. 266). Catalysts that have been found to be effective include Wilkinson s catalyst,229 other rhodium catalysts,230 and iron pentacarbonyl.45 Treatment of /V-allyl amines with Pd(PPh3)4 and (V,(V -dimethylbarbi Lurie acid also cleaves the allyl group.231... 

The reaction of but-l-en-3-yl diethyl phosphate with diethylamine produces N,N-diethylpent-3-enamide (86%), indicating that a Ji-allyl complex is involved in the carbonylation reaction. No isomerism to the a,p-unsaturated amides was observed. 

A recent study has indicated that the skeletal rearrangement step in the B12-catalysed isomerization of methylmalonyl-CoA to succinyl-CoA occurs not by a radical pathway but by an anionic or organocobalt pathway. A computational study of the isomerization of allyl alcohol into homoallyl alcohol by lithium amide has pointed to a process proceeding via a transition state in which the proton is half transferred between carbon and nitrogen in a hetero-dimer. l,l-Dilithio-2,2-diphenylethene... 

In another report of Singh and Han [61], Ir-catalyzed decarboxylative amidations of benzyl allyl imidodicarboxylates derived from enantiomerically enriched branched allylic alcohols are described. This reaction proceeded with complete stereospecificity-that is, with complete conservation of enantiomeric purity and retention of configuration. This result underlines once again (cf. Section 9.2.2) that the isomerization of intermediary (allyl) Ir complexes is a slow process in comparison with nucleophilic substitution. 

An ab initio method has been employed to study the mechanism of the thermal isomerization of buta-1,2-diene to buta-1,3-diene. The results of the study have indicated619 that the transformation proceeds in a stepwise manner via a radical intermediate. Experimental free energies of activation for the bond shift in halocyclooctatetraenes have been reported and analyzed by using ab initio MO calculations.620 The isomerization of hexene using a dihydridorhodium complex in dimethyl sulfoxide has been reported,621 and it has been suggested622 that the Pd(II)-catalysed homogeneous isomerization of hexenes proceeds by way of zr-allylic intermediates. A study has been made623 of alkene isomerization catalysed by the rhodium /-phosphine-tin dichloride dimeric complex, and the double-bond isomerization of olefinic amines over potassium amide loaded on alumina has been described.624... 

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