104308-48-7Relevant academic research and scientific papers
An Experimental and Computational Approach to Understanding the Reactions of Acyl Nitroso Compounds in [4 + 2] Cycloadditions
Chaiyaveij, Duangduan,Batsanov, Andrei S.,Fox, Mark A.,Marder, Todd B.,Whiting, Andrew
, p. 9518 - 9534 (2015/10/12)
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.
C-Nitrosoformamides, a New Class of Transient Dienophiles Formed by Oxidation of N-Hydroxyureas
Christie, Clifford C.,Kirby, Gordon W.,McGuigan, Henry,Mackinnon, John W. M.
, p. 2469 - 2474 (2007/10/02)
Oxidation of hydroxyurea with sodium or tetraethylammonium periodate in the presence of cyclopentadiene gave a cycloadduct (3a) formed, apparently, by capture of the transient dienophile, C-nitrosoformamide.N-Methyl-, N-phenyl-, N,N-dimethyl-, and N,N-diphenyl-C-nitrosoformamide were likewise trapped as their cycloadducts with cyclopentadiene.Cycloadducts of 2,3-dimethylbuta-1,3-diene, thebaine, ergosteryl acetate, and 9,10-dimethylanthracene (DMA) were prepared similarly.The cyclopentadiene adducts (3) dissociated at 80 deg C in the presence of 2,3-dimethylbuta-1,3-diene to give the corresponding adducts (4) of the nitrosoformamides and dimethylbutadiene.Unexpectedly, the 1,4-adducts (4) were accompanied by substantial amounts of hydroxamic acids (5) arising from 'ene' reactions of the nitrosoformamides and dimethylbutadiene.The cyclopentadiene adducts of N,N-dimethyl- and N,N-diphenyl-C-nitrosoformamide, when heated alone, decomposed to give the corresponding carbamic anhydrides.The cycloadduct (15) of DMA and C-nitrosoformamide dissociated at 40 deg C in the presence of thebaine (11) to give the thebaine adduct (12; R=H) and DMA.
