Cyclic allylic amines, oxidation

Furthermore, Stahl and coworkers reported the oxidative amination of cyclic olefin (such as cyclopentene, cycloheptene) to afford cyclic allylic amine product. However, this reaction proceeds via m-am inopal I adation//i-hydride elimination pathway, rather than allylic C-H activation (Scheme 16) [33]. 

Oxidative addition of allylic amines to Ni(0) precursors in the presence of acid has been shown to lead to cationic (allyl)Ni complexes. Thus, Ni(cod)(dppf) reacts with a range of cyclic allylic amines in the presence of trifluoroacetic acid (TFA) to generate complexes 74, as shown in Scheme 22. " This process can proceed by protonation of the amine and the oxidative addition of the resulting ammonium salts, as above. The same system or a mixture of Ni(cod)2 and dppf catalyzes the hydroamination of dienes. In this case, the catalysis is thought to proceed via the initial protonation of Ni(0) precursor to give an Ni-H species that undergoes insertion of the diene to generate an allyl... 

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). 

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]. 

Iron complexes can also catalyze allylic amination [31,32]. Enders et al. have demonstrated the nucleophilic addition of various acyclic and cyclic amines to the optically active l-methoxycarbonyl-3-methyl-(T)3-allyl)-tetracarbonyliron cation 49 formed in high yield from reaction of 48 with iron carbonyls. Oxidative removal of the tetracarbonyliron group by reaction with CAN gives 50 with high optical purity and retention of the stereochemistry (Eq. (12)) [31]. The reaction proceeds well for the different amines, and has been used for the synthesis of a compound showing cytotoxic activity against diverse cell lines [31b]. 

The corresponding ferrilactams (156), which have also been the subject of much attention, are available by the nucleophilic substitution of (155) by amines in the presence of a Lewis acid, usually ZnCb. The substitution occurs with allylic transposition,that is, attack at C-3 of (155). In selected cases, compounds of the type (156) have been prepared by oxidative addition of vinylaziridines or m-4-amino-l-butenols with (2). A bridged ferrilactam bonded through C-2 of the allyl (157) unit has been reported recently and was prepared by way of oxidative addition of a cyclic allylic... 

P-Ketoesters are oxidized at the a-position with oxygen in the presence of either manganese(II) acetate " or cobalt(II) chloride." Cyclic allyl phosphonates give y-acetoxy a,p-unsaturated phosphonates when they are exposed to oxygen in HOAc containing PdCl2 and isopentyl nitrite. " Tertiary amine oxides are formed under cooxidation conditions, that is, O2, Fe203, and isovaleraldehyde. "... 

DMP with high purity by the original procedure therefore, a few modifications have been suggested. In addition, DMP has been successfully used in the syntheses of polycyclic heterocyclesand in the removal of thioketals and thioacetals. It should be mentioned that other hypervalent iodine compounds can be used as oxidants as well, especially for the o-iodoxybenzoic acid (IBX), the precursor to DMP, which can oxidize tertiary cyclic allyl alcohol into O, y0-unsaturated cyclic ketones and secondary amines into imines and can convert epoxides or aziridines into corresponding of-hydroxy ketones or Q -amino ketones. 

Asymmetric allylic amination of allylic carbonates, prepared from racemic MBH adducts, proceeds in the presence of the Pd catalyst chiral diamino-phosphine oxide (DIAPHOX) (292) and BSA to afford the corresponding chiral aza-MBH adduct derivatives 293 in excellent yield with up to 99% ee. The cyclic reaction products could be converted into various synthetically useful compounds, such as chiral cyclic p-amino acids (Scheme 3.119). ... 

Ammonium-directed metal-free oxidation of cyclic allylic and homoallylic amines has been reviewed. Such reactions yield all four diastereoisomers of the corresponding 3-amino-1,2-diols, and have featured in recent syntheses of ( )-l-deoxynojirimycin and ( )-l-deoxyaltronojirimycin. ... 

Intramolecular Hydrosilation of Allyl Amines. The amino group of an allyl amine is silylated with chlorodimethylsilane, and then the resulting silazane is subjected to standard platinum-catalyzed cyclization and oxidation steps to form a syn-2-amino alcohol (eq 1). Exclusive formation of the four-membered cyclic product and the high stereoselectivity should be noted. ... 

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). 

Similar cyclic imines can be synthesized by intramolecular oxidative amination of aminoalkenes, which are less expensive than aminoalkynes. In the presence of catalytic amounts of [RuCl2(CO)3]2/l,3-bis(diphenylphosphino)propane and excess K2C03/allyl acetate, various aminoalkenes 19 possessing substituent(s) f3 to the amino group afforded five- and six-membered cyclic imines 20 in mod-erate-to-excellent yields (Eq. 8) [14]. 

Cyclic ethers and amines can be formed if the nucleophile is an intramolecular alcohol or amine. Stoichiometric palladium can be avoided by using benzoquinone as the stoichiometric oxidant with a catalytic amount of palladium. In this example intramolecular oxypalladation of a diene is followed by attack of an external nucleophile on a TC-allyl complex. 

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