Amines, cyclic, from lactams

Sodium tetrahydridoborate I alcohols Cyclic amines from lactams s. 44, 72... 

The reactions of HN3 with cyclic alcohols to yield mixtures of ketones, amines, and products with an enlarged ring are catalyzed by H2SO4 [1]. Tertiary alcohols are converted to azides in the presence of acid [12] or TiCU [13]. Aldehydes and ketones with HN3 undergo a Schmidt-type reaction by liberating N2 and inserting NH In the presence of H or Lewis acids [14]. Ketones yield secondary amides and, in the case of cyclic ketones, lactames. Aldehydes are converted to nitriles or N-formylamines. Tetrazole derivatives result with excess HN3 [1, 15]. However, a-azido ethers are obtained from aldehydes and HN3 in the presence of alcohols by catalysis of TiC [16]. Carboxylic acids and anhydrides form amines, N2, and CO2 in Schmidt reactions with HN3. Intermediates are carbamic acids which form by insertion of NH into the R-COOH bond [1, 14]. High yields result for acids of arenes [17]. 

The cyclic carbonate of benzoin (4,5-diphenyl-l,3-dioxol-2-one, prepared from benzoin and phosgene) blocks both hydrogen atoms of primary amines after dehydration acid stable, easily crystallizable Sheehan oxazolinones are formed, which are also called Ox derivatives. The amine is quantitatively deblocked by catalytic hydrogenation in the presence of 1 equiv. of aqueous acid (J.C Sheehan, 1972, 1973 M.J. Miller, 1983). An intelligent application to syntheses of acid labile -lactams is given in the previous section (p. 161). 

The lactam formation from the oxidation of cyclic amines (353, for example) probably proceeds via intermediate 364. The nitrogen-iodine bond dissociates to give imine 365, which reacts again with a second equivalent of iodosobenzene to give another intermediate 366. Finally, 366 on reductive... 

Similarly, both acyclic and cyclic allyl amine derivatives have been applied in 1,3-dipolar cycloadditions (134-138). Langlois et al. (139) used a,()-unsaturated-y-lactams derived from (5)-pyroglutaminol, such as 91 and 92, in the 1,3-dipolar cycloaddition with the A -benzylnitrone derived from formaldehyde (Scheme 12.30). For compound 91, one of the 1,3-dipolar cycloaddition product isomers obtained... 

A nitrogen analog of J72 was also studied (56). The amino-diester 176, upon release from its stable hydrochloride salt, rapidly closed at 25°C to the lactam 177 (100%) via the favored 5-Exo-Trig pathway. The disfavored 5-Endo-Trig process yielding the cyclic amino-diester 178 was not observed. On the other hand, it is known that primary amines undergo a 1,4-addition to a-substituted acrylic esters (179 -> 180) more rapidly than they are acylated to the a-substituted acrylamides (179 ->181). 

Although it is reported that the U-5C-4CR can work well with nucleophiles other than methanol, such as primary or secondary amines, the only examples reported in the literature are those where trifunctional a-aminoacids such as lysine [67] or homoserine [66] or bifunctional aldehydes such as glycolaldehyde [65] are employed. In these cases, the side-chain amino or hydroxy group acts as the nucleophile and opens the cyclic intermediate generating the corresponding lactams or lactones. A less nucleophilic solvent such as trifluoroethanol is usually employed, in order to maximize the intramolecular attack. The observed stereoselectivities are, apart from a few examples [66], usually not very high this could be due to different factors (a) the side chains of the a-amino acids are not very bulky (b) the intramolecular nucleophilic attack could be faster than the methanol attack and the cyclic intermediate could not equilibrate to the thermodynamically favored isomer (c) the intramolecular nucleophilic attack on the more stable diastereoiso-meric cyclic intermediate could be kinetically less favored. 

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). 

Early attempts to extend the halolactonization procedure to yield lactams gave cyclic imidates instead, but several approaches favor lactam products. These include working with silyl imidates, imidate esters or oxazolines, using sulfonylcarbamates or other acidic amides or by using hydroxyl-amine derivatives with increased nucleophilicity due to the a-effect. Lactams can also be favored as a consequence of steric requirements. In a few cases, amines can be cyclized to cyclic amines many lead references are given in a recent report on cyclic hydroxylamines such as (64). Veiy recent work has provided a fairly general iodolactamization procedure from unsaturated amides, trimethylsilyl triflate and iodine (Scheme 89). ... 

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