70156-86-4

Tetrabutylammonium decatungstate (TBADT) has emerged as a valuable photocatalyst for sunlight-induced organic reactions. In this communication we wish to present its use for the photocatalytic oxidation of hydroxamic acids to generate fleeting nitrosocarb

[Bis(trifluoroacetoxy)iodo]benzene (BTI) and (diacetoxyiodo)benzene (DIB) efficiently promote the formation of acylnitroso species from hydroxamic acids in the presence of various dienes to give the corresponding hetero-Diels-Alder (HDA) adducts in moderate to high yields. The present method could be applied to the HDA reactions of acylnitroso species with o-benzoquinones generated by the oxidative dearomatization of guaiacols.

As a first non-metal-catalyzed oxidation for the in situ generation of acylnitroso species, we describe the hypoiodite catalysis using tetra-n-butylammonium iodide as precatalyst with tert-butyl hydroperoxide or hydrogen peroxide as a terminal oxidant. Th

Background: Acylnitroso intermediates are considered as highly reactive and useful transient that have been used to synthesize a broad class of biological active compounds and synthetic drugs. Although there are some reported methods for the generation of these intermediates, but still challenge for mild and environmental benign protocol. Herein, we report the facile in situ synthesis of acylnitroso intermediates and their efficient hetero Diels-Alder (HDA) and ene reactions. Methods: Acylnitroso intermediates were readily obtained by hydrogen peroxide oxidation of hydroxamic acids catalyzed by Cu(I)-, Ir(I)- or Ru(II)-complexes and easily reacted with symmetric and asymmetric conjugated dienes beside their reaction with different alkenes which converted to biological active products. Results: The resulted acylnitroso intermediates were efficiently afforded the hetero Diels-Alder cycloadducts in the presence of cyclopentadiene, cyclohexadiene or α-terpinene in high yields along with good regioselectivity for the later. In case of N-dienyl lactams, the cycloadducts were formed in the yield up to 89% with complete regioselectivity. In the presence of optically active N-dienyl pyroglutamates, diastereoisomers were formed in high yields with up to 72 de. In addition, the transient acylnitroso species were trapped with alkene to form the ene product in yield up to 95 %. As an interesting transformation, the halocyclization of the ene products gave substituted oxazolidone in 77% yield which considered as one of the effective antimicrobial and antibiotic compounds. Conclusion: In a brief, we introduce a mild and effective route to deliver acylnitroso intermediates in situ by using environmentally benign, cost effective, and non-toxic hydrogen peroxide oxidant catalyzed by Cu(I)-, Ir(I)- or Ru(II)-complexes. Good to excellent yields, regio- and diastereoselectivity were obtained by trapping these intermediates in symmetric and asymmetric HDA and ene reactions. Interestingly, the ene products easily transformed to potent drugs.

Catalytic aerobic oxidation of phenyl hydroxycarbamate 1 and 1-hydroxy-3-phenylurea 2 using CuCl2 and 2-ethyl-2-oxazoline in methanol gave acyl nitroso species in situ, which were trapped in nitroso-Diels-Alder (NDA) reactions with various dienes to afford the corresponding cycloadducts in high yields (90-98%). Competing ene products were also present for dienes containing both alkene π-bonds and allylic σ-bonds, and the ene yields are higher with 1 than with 2. The use of the chiral hydroxamic acid, (R)-1-hydroxy-3-(1-phenylethylurea) 3 (same conditions) gave NDA cycloadducts in high yields (97-99%) with no ene product from 2,3-dimethyl-1,3-butadiene. NDA cycloadducts were not obtained from other hydroxamic acid analogues [RCONHOH (R = PhCH2 4; Ph(CH2)2 5; Ph(CH2)3 6; Ph(CH2)4 7; Ph 8; 2-pyridyl 9; 3-pyridyl 10] with various dienes using copper-oxidation but rather were obtained using sodium periodate, resulting in variable NDA yields (13-51%) from hydroxamic acids 1-10 with cyclohexa-1,3-diene and 2,3-dimethyl-1,3-butadiene (several cycloadducts characterized by X-ray crystallography). The NDA and nitroso-ene reaction pathways of nitroso intermediates with dienes were mapped by DFT computations (B3LYP/6-31G), which showed that the acyl nitroso species are super-reactive and that activation energies in the NDA processes are lower than the isomerization barriers between some cis- and trans-butadienes.

A general and efficient aerobic oxidation of N-substituted hydroxylamines is described. The mild reaction conditions employed provide a catalytic and sustainable alternative to stoichiometric oxidation methods to gain access to a range of nitroso compound

Benzoyl nitroside (5) was generated in solution by laser photolysis of 3,5-diphenyl-1,2,4-oxadiazole-4-oxide (4) and studied by time-resolved infrared spectroscopy. The second-order rate constantsfor reaction of 5 with diethylamine and 1,3-cyclohexadiene were determined to be (1.3 ± 0.5) × 105 M-1 s-1 and (6.0 ± 0.5) × 103 M-1 s-1, respectively. The formation of nitroxyl (HNO), a product of the reaction of 5 with diethylamine, was also observed. Copyright

The oxidation of hydroxamic acids, N-hydroxyureas and N- hydroxycarbamates with the Dess-Martin periodinane generates the corresponding acyl nitroso compounds that react with conjugated dienes to produce the corresponding cycloadducts.

Nitrosocarbonyl intermediates are photochemically generated from 1,2,4- oxadiazole-4-oxides and efficiently trapped with enes and dienes.

Nitrile oxides are oxidized by tertiary amine N-oxides in different solvents at room temperature to afford in the presence of dienes nitrosocarbonyl adducts in fair yields. The mild conditions used in oxidizing a variety of nitrile oxides promise a wide application of this method in synthetic processes.

Addition of N-methyl morpholine N-oxide (NMO) to a nitrile oxide solution in dichloromethane at room temperature in the presence of a diene affords nitroso carbonyl adducts in fair yields.

The synthesis of simple nortropane and nortrop-6-ene derivatives from cyclohepta-1,3-diene is described.The key intermediates are trans-1-amino-4-chloro-cycloheptanes and -cyclohept-2-enes which are derived efficiently from the corresponding cis-amino-alcohols and undergo intramolecular cyclisation.Corresponding derivatisation of cyclohexa- and cycloocta-1,3-dienes is explored and attempts to achieve Pd-catalysed cyclisation of 1-amino-4-acetoxy-derivatives is described.Nitrogen inversion data for selected nortropane derivatives are included. Key Words: nortropanes/enes; 1,4-disubstitute cyclohexanes, cycloheptanes, cyclooctanes and -enes; intramolecular cyclisation; slow nitrogen inversion.

Nitrosocarbonylbenzene and nitrosocarbonylmethane, formed as transient intermediates by oxidation of benzo- and aceto-hydroxamic acid, respectively, with tetraethylammonium periodate, are trapped by cyclopentadiene to give the corresponding cycloadducts (5).The adduct (5; R=Ph) dissociates in solution at 80 deg C to reform nitrosocarbonylbenzene, which reacts with thebaine (1) to give (4; R=Ph) and with triphenylphosphine to give phenyl isocyanate.Cycloadducts of nitrosocarbonylbenzene with cyclohexa-1,3-diene (6) and with cyclo-octatetraene (7) have also been prepared.The adduct (3; R=Ph) of nitrosocarbonylbenzene and 9,10-dimethylanthracene, when heated with 1-allyl-3,4-methylenedioxybenzene, oct-1-ene, or 2,5-dimethylhexa-2,4-diene, gives the corresponding 'ene' reaction products of the olefins and nitrosocarbonylbenzene.When heated alone, the adduct (3; R=Ph) gives 9,10-dimethylanthracene, benzoic anhydride, and nitrous oxide.Oxidation of 2,4,6-trimethylbenzohydroxamic acid in the presence of thebaine gives the adduct (4; R=2,4,6-trimethylphenyl).However, 2,4,6-trimethylnitrosocarbonylbenzene is insufficiently stable to be isolated; in the absence of a diene it decomposes to give 2,4,6-trimethylbenzoic anhydride as the major product.

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