Cyclic amines, rearrangements with

The reaction of the vinylcyclopropanedicarboxylate 301 with amines affords an allylic amine via the 7r-allylpalladium complex 302[50]. Similarly, three-membered ring A -tosyl-2-(l,3-butadienyl)aziridine (303) and the four-mem-bered ring azetidine 304 can be rearranged to the five- and six-membered ring unsaturated cyclic amines[183]. 

A related amination/rearrangement/cyclization tandem sequence had been introduced by Cossy [49]. Starting from cyclic epoxyketones 224 the reaction with propargylamines 225 caused an oxirane-opening condensation process to generate the enaminoketones 226. Upon heating in toluene to reflux, aza-Claisen rearrangement delivered the intermediate allenyl imines 227, which... 

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. ... 

The cyclohexene 121, which was readily accessible from the Diels-Alder reaction of methyl hexa-3,5-dienoate and 3,4-methylenedioxy-(3-nitrostyrene (108), served as the starting point for another formal total synthesis of ( )-lycorine (1) (Scheme 11) (113). In the event dissolving metal reduction of 121 with zinc followed by reduction of the intermediate cyclic hydroxamic acid with lithium diethoxyaluminum hydride provided the secondary amine 122. Transformation of 122 to the tetracyclic lactam 123 was achieved by sequential treatment with ethyl chloroformate and Bischler-Napieralski cyclization of the resulting carbamate with phosphorus oxychloride. Since attempts to effect cleanly the direct allylic oxidation of 123 to provide an intermediate suitable for subsequent elaboration to ( )-lycorine (1) were unsuccessful, a stepwise protocol was devised. Namely, addition of phenylselenyl bromide to 123 in acetic acid followed by hydrolysis of the intermediate acetates gave a mixture of two hydroxy se-lenides. Oxidative elimination of phenylselenous acid from the minor product afforded the allylic alcohol 124, whereas the major hydroxy selenide was resistant to oxidation and elimination. When 124 was treated with a small amount of acetic anhydride and sulfuric acid in acetic acid, the main product was the rearranged acetate 67, which had been previously converted to ( )-lycorine (108). 

Cyclic carbonates react with primary amines to give /3-oxo carbamates which are dehydrated to 2(3//)-oxazolones (equation 141). Thermal rearrangement of the isoxazolone (290) results in the oxazolone (291 equation 142). 

Allylic alcohols are reduced with lithium or sodium in ammonia, or low molecular weight amines either with or without alcohols. The thermodynamically more stable product is often formed, leading to rearrangement in some cases (equation 71). Methyl and cyclic ethers are similarly reduced (equations 72 and 73), as are allylic acetates, halides and epoxides (equation 74 and 75). 7.i08 Benzylic and allylic sulfides and sulfones are readily reduced to hydrocarbons using lithium or sodium in alcoholic solvents or in amines. " Allylic sulfones are reduced in a similar manner (Scheme 11)," either with or without migration of the double bond, depending on the reaction conditions used. 

In an extension of earlier work, Buigada et al. have also reported on the reaction of the cyclic phosphite (66) with dimethylacetylene dicarboxylate (58) in the presence of proton sources such as carboxylic acids, amide N-H bonds in succinimide or phthalimide and amine N-H bonds in p UTole or indole. With carboxylic acids (67) a mixture of the ylid (68) and the cyclic phosphorane (69) was obtained and in some instances (e.g. with 2,4,6- trimethylbenzoic and p-methoxybenzoic acids) the ylid and phosphorane were shown to be in equilibrium. With amides as the proton source, ylids were generally formed although with N-methylbenzamide (PhCONHMe)a signal attributed to (70) was observed at = - 52 p.p.m. which had disappeared by the end of the reaction through rearrangement to (71). With amines (e.g. pyrrole) the products were again a mixture of ylid (72) and phosphorane (73) and the entire set of results was rationalised in terms of HSAB theory and the symbiotic effect around phosphorus. 

The base-induced 2,3-shift in a benzyltrialkylammonium halide (Sommelet-Hauser synthesis) efrects an orr/io-selective aminomethylation of aromatics. A variation (orr/to-selective formylation) is shown in equation (37). Unfortunately, the 1,2-Stevens rearrangement (— 10% 143) of the intervening ylide competes with the 2,3-pathway (— 142). A reliable tool to circumvent this very general difficulty is still unknown. Nonetheless, 2,3-rearrangement pathways can be very efficient as demonstrated by the synthesis of the cyclic amine (144 equation 38). ... 

Rickborn and co-workers ° ° isolated the cycloadduct 164 from 4-phenylox-azole through careful manipulation of the experimental conditions (Fig. 3.50). They generated benzyne at 0°C from 1-aminobenzotriazole and lead tetraacetate. Compound 164 was stable at room temperature but, on heating, eliminated benzo-nitrile to give isobenzofuran 162, which could be trapped with A -methylmaleimide to afford a quantitative yield of the tetracyclic derivative 166 as an 88 12 mixture of endo and exo isomers. The cyclic aminal 164 was also sensitive to acid and rearranged to 4-hydroxy-3-phenyl-isoquinoline 165 on exposure to silica gel or a catalytic amount of trifluoroacetic acid. The benzyne cycloadditions were also carried out on 4-(4-nitrophenyl)oxazole and 4-(4-methoxyphenyl)oxazole. A fourfold rate increase was seen for the cycloaddition of the nitrophenyl-substituted oxazole relative to the methoxyphenyl analog, indicating a concerted process with little contribution from a polar intermediate. 

The [2,3]-rearrangement of amine iV-oxides was utilized in an efficient S5mthesis of 2,6-dimethyl-l,5-heptadien-3-ol acetate 61, a pheromone of the insect Pseudococcus comstocki tScheme lS.12id Dimethylpyridine 55 was converted in two steps into silylated piperidine 56, which was oxidized with m-CPBA to generate cyclic amine A-oxide 57. Sila-Cope elimination furnished O-silylhydroxylamine 58, which was methylated and desilylated in the presence of Mel and CsF to yield acyclic amine A-oxide 59. Heating this ammonium zwitterion facilitated the [2,3]-Meisenheimer rearrangement to O-allylhydroxylamine 60, which was transformed to the desired pheromone 61 in three steps. 

The role of acid-promoted palladium-catalysed isomerization in the skeletal rearrangement of cyclic amines has been reported. A palladium-catalysed tunable functionalization of allylic imidates, including regioselective aminodiacetoxylation and aziridination with switchable reactivity towards divergent C—N and C—O bond formation, has been reported (Scheme 137). ... 

Subsequent experiments showed that piperidine with D-fructose gave D-glu-cose, and that morpholine, dicyclohexylamine as well as tertiary amines converted D-fructose into D-psicose without detectable formation of Heyns rearrangement products. Employing secondary amines such as pyrrolidine, the corresponding Heyns rearrangement products could be obtained very easily, contrasting results with other cyclic amines, for example, piperidine, hexame-thylene imine (azepane) and other open-chain amines such as dimethyl-, diethyl-, or methylbenzylamine, which did not react [105]. 

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