Amines allylic, reduction

O-Methanesulphonyloximes of a,/i-unsaturated ketones yield allylic amines on reduction with lithium aluminium hydride (equation 78)207. 

Primary ally lie amines1 In the presence of this catalyst, allylic chlorides or acetates react with sodium p-toluenesulfonamide in THF/DMSO (80 20) to form the corresponding allylic sulfonamide in 60-85% yield. The products are converted into primary allylic amines on reductive cleavage (sodium naphthalenide). 

Borohydride reduced Pd is also a versatile hydrogenation catalyst that effects the partial reduction of multifunctional unsaturated compounds selectively. It can reduce the w-bond of C=C, N=N, N=0, but not the w-bond of C=N, C=0, nor the --bond of C— N, C—O. Allylic alcohols, allylic amines, allylic ethers, a-methylstyrene, acrylamide, 3-butene nitro, and also mesityl oxide, crotonaldehyde, and maleic anhydride are among the selectively reduced substrates. ... 

The reaction with Af-Boc protected allyl amine was carried out in a 10 mmol scale with a ratio of substrate/Rh = 10 000 1 for 24 h without affecting the regio-and stereochemistry found in the prehminary screening (Scheme 4.79). The iV-mono-protected P -amino aldehyde was converted into the corresponding P -amino carboxylic acid by oxidation or into the corresponding 1,3-hydroxy amine by reduction. Both are valuable chiral building blocks. 

Based on the above-mentioned stereochemistry of the allylation reactions, nucleophiles have been classified into Nu (overall retention group) and Nu (overall inversion group) by the following experiments with the cyclic exo- and ent/n-acetales 12 and 13[25], No Pd-catalyzed reaction takes place with the exo-allylic acetate 12, because attack of Pd(0) from the rear side to form Tr-allyl-palladium is sterically difficult. On the other hand, smooth 7r-allylpalladium complex formation should take place with the endo-sWyWc acetate 13. The Nu -type nucleophiles must attack the 7r-allylic ligand from the endo side 14, namely tram to the exo-oriented Pd, but this is difficult. On the other hand, the attack of the Nu -type nucleophiles is directed to the Pd. and subsequent reductive elimination affords the exo products 15. Thus the allylation reaction of 13 takes place with the Nu nucleophiles (PhZnCl, formate, indenide anion) and no reaction with Nu nucleophiles (malonate. secondary amines, LiP(S)Ph2, cyclopentadienide anion). 

The formation of an enamine from an a,a-disubstituted cyclopentanone and its reaction with methyl acrylate was used in a synthesis of clovene (JOS). In a synthetic route to aspidospermine, a cyclic enamine reacted with methyl acrylate to form an imonium salt, which regenerated a new cyclic enamine and allowed a subsequent internal enamine acylation reaction (309,310). The required cyclic enamine could not be obtained in this instance by base isomerization of the allylic amine precursor, but was obtained by mercuric acetate oxidation of its reduction product. Condensation of a dihydronaphthalene carboxylic ester with an enamine has also been reported (311). 

Olefins are also the products of hydroboratlon of enamines, followed by treatment of the organoborane products with hot acid (543,544). The reduction of enamines with sodium borohydride and acetic acid (545) and the selective reduction of dienamines with sodium borohydride to give homo-allylic tertiary amines (138-140,225,546,547), has been applied to the synthesis of conessine (548) and other aminosteroid analogs (545,549-552). Further examples of the reduction of imonium salts by sodium borohydride can be found in the reduction of Bischler-Napieralski products, and other cyclic imonium salts (102). 

The first of the nudeophilic ring-opening reactions of vinylaziridines discussed in this section is diborane reduction, developed by Laurent and coworkers in 1976 (Scheme 2.24). Treatment of N-unsubstituted vinylaziridines 89 with B2H6 gives allyl amines 92 by SN2 reduction via cyclic intermediates 90 [40]. In contrast, treatment with 9-BBN gives 2-(hydroxyethyl)aziridines 93 after oxidative workup (Scheme 2.25) [41]. 

Subsequently, Julia, Uguen and Callipolitis104 105 used both lithium metal in ethyl-amine and sodium amalgam in ethanol to effect reductive cleavages of j8-hydroxysulphones or of allylic sulphones. The latter reaction is part of a synthetic sequence for the construction of alkenes that has been used with some considerable success... 

Reduction of iV-(3-bromopropyl) imines gives a bromo-amine in situ, which cyclizes to the aziridine. Five-membered ring amines (pyrrolidines) can be prepared from alkenyl amines via treatment with N-chlorosuccinimide (NCS) and then BusSnH. " Internal addition of amine to allylic acetates, catalyzed by Pd(PPh3)4, leads to cyclic products via a Sn2 reaction. Acyclic amines can be prepared by a closely related reaction using palladium catalysts. Three-membered cyclic amines (aziridines)... 

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