R. Michael Paton

Para-selective fries rearrangement of phenyl acetate in the presence of zeolite molecular sieves

Abstract The Fries rearrangement of phenyl acetate is catalysed by acidic zeolites such as H-Nu-2 and H-ZSM-5, with selectivities of 2-6:1 in favour of para-substituted products.

Highly selective base-catalysed additions of nitromethane to levoglucosenone

Abstract Nitromethane undergoes base-catalysed addition to levoglucosenone affording 2:1 and 1:2 adducts (2) and (7) in high yield (≥ 95%); the products result from initial Michael addition exclusively at the exo-face of the alkene anti to the 1,6-anhydro bridge.

Generation and cycloaddition reactions of pyranose-1-carbonitrile oxides

Stannate(II) reduction of the β-d-glucopyranosylnitromethane derivative 4 affords aldoxime 5, which provides access to the nitrile oxide 7, either on treatment with aq. hypochlorite, or via conversion to the hydroximoyl chloride 11 followed by base-mediated dehydrohalogenation. d-Galactose-, d-mannose- and d-xylose-derived nitrile oxides are generated similarly. The nitrile oxides either dimerise to 3,4-dipyranosyl-1,2,5-oxadiazole N-oxides or are trapped as cycloadducts in the presence of dipolarophiles.

1,3-dipolar cycloaddition reactions of levoglucosenone

Abstract The cycloaddition reactions of levoglucosenone with various 1,3-dipoles have been examined. Benzonitrile oxide underwent regiospecific and face-selective cycloaddition yielding isoxazoline 2a as the major product. D-Glyceraldehyde-derived nitrile oxide 6 was less selective and afforded furazan N-oxide dimer 8 in addition to a mixture of isoxazolines. C,N-Diphenylnitrone and N-benzyl-C-phenylnitrone reacted similarly yielding isoxazolidines 9 and 10. In each case the major adduct resulted from attack at the less hindered face of the dipolarophile anti to the 1,6-anhydro bridge, and with the oxygen of the nitrile oxide or nitrone becoming attached to the β-carbon of the enone. In contrast benzonitrile N-phenylimide added to levoglucosenone to give a regioisomeric mixture of pyrazoles 11 and 12, resulting from dehydrogenation in situ of the initially formed pyrazolines. No reaction was observed with p-methoxybenzonitrile sulphide. The structures of isoxazoline 2a and isoxazolidine 9 were confirmed by X-ray crystallography.

3,4-Dipyranosyl-1,2,5-oxadiazole 2-oxides: synthesis and X-ray structure

Abstract 3,4-Di(2,3,4,6-tetra-O-acetyl-β- d -mannopyranosyl)-1,2,5-oxadiazole 2-oxide ( 7 ) has been synthesised from d -mannose by a route involving as the key step dimerisation of mannopyranosyl nitrile oxide 2 . Three methods were used for the generation of the nitrile oxide: isocyanate-mediated dehydration of nitromethylmannose derivative 4 , treatment of aldoxime 5 with aq. hypochlorite, and base-induced dehydrochlorination of hydroximoyl chloride 6 . d -Gluco, d -galacto, d -xylo, and l -fucopyranosyl analogues 8–11 were prepared similarly. The structure of d -mannose-derived 1,2,5-oxadiazole 2-oxide 7 was established by X-ray crystallography.

Isolation of nitrile oxides from the thermal fragmentation of furazan N-oxides

Flash vacuum pyrolysis of furoxans generates nitrile oxides, which have been reacted with alkenes to yield 2-isoxazolines, and have been examined by 1H and 13C nmr spectroscopy.

Microwave‐Assisted Generation and Reactions of Nitrile Sulfides

Abstract An improved practical method is described for the generation of benzonitrile sulfide based on microwave‐assisted decarboxylation of 5‐phenyl‐1,3,4‐oxathiazol‐2‐one. Reaction times for the preparation of cycloadducts (e.g. isothiazoles and 1,2,4‐thiadiazoles) derived from the nitrile sulphide are reduced from typically 15–30 h to approximately 15 min.

Synthesis of (1→6) linked C-disaccharide derivatives using nitrile oxide/isoxazoline chemistry

Abstract A stereocontrolled route to (1→6)-hydroxymethylene-linked C -disaccharide derivatives has been developed based on cycloaddition of pyranose 1-carbonitrile oxides to 5,6-dideoxyhex-5-enofuranoses and reductive hydrolytic cleavage of the resulting 2-isoxazolines.

Stereoselective cycloaddition of nitrile oxides to 4-vinyl-oxazolines and -oxazolidines

Abstract Cycloaddition of nitrile oxides to 4-vinyl-2-oxazoline 1 and to 4-vinyloxazolidine 2 afford diastereomeric mixtures of 2-isoxazolines in which the erythro product predominates (32–64% d.e.). In contrast, the corresponding reactions with acyclic analogue 3 favoured the threo-adducts and were less selective (8–20% d.e.).

Divergent behaviour in the isocyanate-induced and thermal generation of nitrile oxides from ethyl nitroacetate

Abstract Ethyl nitroacetate is a source of three nitrile oxides: thermolysis results in elimination of ethanol and carbon dioxide to generate formonitrile oxide (HCN + O - ), whereas treatment with phenyl isocyanate and a base gives either ethoxy-carbonylformonitrile oxide (EtO 2 CCN + O - ) or cyanoformanilide N -oxide (PhNHCOCN + O - ) depending on the reaction conditions.