Benzylamine rearrangement

The most prominent examples of this type of reaction are the Fischer Indole synthesis, the Beckmann rearrangement and the benzylamine rearrangement. For all three reactions rather complex mechanisms have been proposed. On comparing the structure- activity relationships for these transformations, it becomes clear that generalisations are difficult and that a complex interplay between pore shape and size, the acid strength and the polarity of the zeolite lattice seems to control the activity and selectivity for a given reaction. 

In 1997 the first asymmetric aza-Claisen rearrangement was reported by Overman et al. [55], which made use of diamines as bidentate ligands for Pd(II), allowing for moderate enantioselectivities. In the same year, Hollis and Overman described the application of the planar chiral ferrocenyl palladacycle 38 as a catalyst for the enantioselective aza-Claisen rearrangement of benzimidates 39 (Fig. 19) [56]. A related ferrocenyl imine palladacycle provided slightly inferior results, while a benzylamine palladacycle lacking the element of planar chirality was not able to provide any enantioselectivity [57]. 

Aryl alkyl amines gave hydroxylamine 0-arylsulfonates when reacted with arylsul-fonyl peroxide. The products were later decomposed to azomethine and further hydrolysis results in the corresponding amine with one less carbon atom. Thus when p-methoxy-benzylamine was treated with p-nitrophenylsulfonyl peroxide at —78 °C in ethyl acetate, p-methoxybenzaldehyde and p-methoxyaniline were obtained . Cyclic amines with p-nitrophenylsulfonyl peroxide were converted to the Al-(p-nitrophenylsulfonyloxy)amine derivatives, which further rearranged to ring-expanded cyclic imines in good yields (equation 9 f. ... 

A syn displacement of the bromine by benzylamine in the presence of triethylamine led, by a Sn2 reaction, to the a and p amino compounds which were separated into 326 (18%) and 327 (81%) respectively. The dichloroacetamide 328 derived from the latter, when subjected to the action of tri-n-butyltinhydride (2eq) and 2,2 -azobisisobutyronitrile underwent a 5-ero ring closure to furnish via the radical 329, the hydrooxindole 330 (51%) and significant amount of the rearrangement product 331 (30%). The latter is believed to be formed by fragmentation of the cyclohexadienyl radical 332 generated from the cyclohexyl radical 329. On diborane reduction, 330 provided the cis hydroindole 333, which on 0,N-debenzylation afforded ( )-c -fused bicyclic aminoalcohol 334, a compound that had been previously cyclised with formaldehyde to ( )-elwesine (320) by Stevens et al [85]. 

Carbon-13 n.m.r. spectroscopy has been used to study benzylisoquinoline and tetrahydroisoquinoline alkaloids and their JV-methyl quaternary salts.30 N-Benzylpapaverinium bromide has been shown to undergo aerial oxidation in alkaline solution to 2-benzyl-6,7-dimethoxyisoquinolone and to give bases of general structure (10) with methylamine, benzylamine, and pyrrolidine.31 Chlorosulphonation of papaverinol affords the sulphonic acid ester (11), mild hydrolysis of which yields the acid (12), which with diazomethane is esterified and dehydrated to (13).32 N-Methyl-l,2-dihydropapaverine has been shown by kinetic studies and orbital-symmetry requirements to rearrange to the salt (14) by the route previously postulated.33... 

Based on a previous study by Miller,289 a series of iV-benzyl-MSMA chlorides or bromides have been treated with a base and/or a nucleophile. For example, in the presence of the amide anion, the trimethylsilyl derivative yields iV,/V-dimethyl-2-methyl-a-(trimethylsilyl)benzylamine (a Sommelet-Hauser rearrangement product) as the main... 

Sc(OTf)3 also catalyzes acetalization reactions [47a,b], acylal formation [47c], /9-selective glycosilation reactions with thioglycosides [48], and acylation reactions of alcohols [49]. Guanidium formation reactions of carbodiimide with benzylamine [50], intermolecular stereoselective radical additions to A/-enoyloxazolidinones [51], and rearrangement of... 

Condensation of an a, -unsaturated ketone with benzylamine gives the corresponding Schiff base. Treatment with a base such as potassium r-butoxide affects rearrangement to a benzaldehyde derivative, as shown in Scheme 82. Hydrolysis of the latter with dilute acetic acid furnishes the corresponding saturated ketone with concomitant formation of benzaldehyde. 

A migration of an aryl group from carbon to nitrogen takes place also in the Stieglitz rearrangement. For example, the benzylamine derivatives 234 were converted into anils 235 in a reaction induced by p-nitrobenzenesulfonyl peroxide (p-NBSP)337 (equation 94). 

Cluisen rearrangement of allyloxyanthraquinones.1 Benzylamine is an effective catalyst for rearrangement of 1 to 2. The yield is increased, the reaction proceeds at... 

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