Ian Gosney

Preparation and properties of some stable arsonium ylides

Abstract Stable crystalline arsonium ylides have been prepared by thermal decomposition of diazo compounds in the presence of triphenylarsine, and by condensation reactions of reactive methylene compounds with triphenylarsine oxide. The spectra of these ylides, and their reactions with benzaldehydes are discussed. Like other stabilised arsonium ylides they give alkenes rather than epoxides in Wittig reactions. They are generally more polar than their phosphonium analogues and also are more reactive in the Wittig reaction. With diphenylcyclopropenone some more reactive arsonium ylides form α-pyrones.

Enantiospecific preparation of (2R,6S)-endo]-5-aza-1,10,10-trimethyl-3-oxatricyclo[5.2.1.02,6]decan-4-one by a nitrene-mediated route from [(1S)-endo]-(-)-borneol and its utility as a chiral auxiliary in some asymmetric transformations

Abstract Attempted chiral aziridination of styrene by addition of optically-active alkoxycarbonylnitrene 5 derived from [(1 s )-endo]-(−)-bornyl-p-nitrobenzenesulphonoxycarbonate 4 is reported. No measurable asymmetric induction is observed under the various conditions employed, but in the absence of alkene, a tricyclic oxazolidin-2-one 8 is formed to which preparatively simpler access can be gained by thermal decomposition of azidoformate 7, either in 1,1,2,2-tetrachloroethane (50%) or by spray pyrolysis (58%). The oxazolidin-2-one 8 is demonstrated to be a successful chiral auxiliary by contemporary standards in a variety of asymmetric transformations, including alkylation, acylation, and aldol reactions for which high levels of asymmetric induction are observed. Diethylaluminium chloride-catalysed Diels-Alder reactions exhibit poorer selectivity except for the cinnamoyl derivative 23 which is stereospecific.

Chemical transformations on the surface of [60]fullerene: Synthesis of [60]fullereno[1′,2′:4,5]oxazolidin-2-one

Abstract Base-induced α-elimination from substituted O -4-nitrophenylsulfonylhydroxamic acids has been used as a mild source of nitrenes for capture by [60]fullerene; rearrangment of the resulting [60]fullereno[1′,2′:2,3]aziridine bearing a N -ethoxycarbonyl grouping under the influence of phenol/chlorotrimethylsilane results in the quantitative formation of the title compound which can be cleaved to yield 1-hydroxy-2- N -methylamino[60]fullerene.

Aziridino[2′,3′ : 1,2][60]fullerene

Thermal elimination of isobutene and CO2 from N-tert-butoxycarbonylaziridino[2′,3′ : 1,2][60]fullerene 4 provides a clean and efficient route to aziridino[2′,3′ : 1,2][60]fullerene 1, an isolable and stable solid.

Bis-functionalisation of C60via thermal rearrangement of an isolable fulleroaziridine bearing a ‘solubilising’ supermesityl ester moiety

Heating of C60 with the novel azidoformate 3 bearing a highly solubilising supermesityl group affords the first example of a nitrogen-bridged fullerene 4, with a σ-homoaromatic closed 6,6-aziridine structure, which by further heating can be induced to undergo rearrangement on the fullerene surface to form as the sole product, the closed isomeric oxazole derivative 5 with O and N vicinally bound to the fullerene framework at a 6,6-ring juncture

Asymmetric Diels-Alder reactions employing modified camphor-derived oxazolidin-2-one chiral auxiliaries

Abstract Transposition of the dormant methyl group from C-1 in chiral oxazolidin-2-one 2 to C-7 in a six step synthetic sequence from (1R)-camphor 5 creates a novel transfigomer 4 with sufficient π-topological bias to induce excellent levels of asymmetric induction in Lewis-acid catalysed Diels-Alder reactions of its α, β-unsaturated carboximide derivatives with cyclopentadiene. Further modification of 4 by replacement of the C-7 methyl group with an ethyl substituent raises the level of diastereoselectivity for the acrylate derivative 11a from 81 to >95% d.e..

A concise synthesis of (−)-Dihydroprotolichesterinic acid via consecutive stereocontrolled 1,4-conjugate addition and syn-aldol condensation reactions

(−)-Dihydroprotolichesterinic acid 1a is synthesised in 6 steps and 57% overall yield by a strategy employing the camphene-derived chiral auxiliary 2 to construct the three contiguous stereogenic centres in consecutive stereocontrolled 1,4-conjugate addition and syn-aldol reactions.

Highly regio- and stereo-specific preparation of a new carbohydrate-based 1,3-oxazin-2-one by the INIR method and its applications in some asymmetric transformations

Abstract Preliminary experiments show that a new gulonic acid-derived 1,3-oxazin-2-one, prepared by an intramolecular nitrene insertion reaction (INIR) method, serves to control both asymmetric aldol and Diels-Alder reactions with excellent stereo-selection.

Birch reduction of C60—a new appraisal

Contrary to a previous report that Birch reduction of C60 affords C60H36 as the principal product, laser desorption-laser photoionisation time-of-flight (L2TOF), laser desorption Fourier transform ion cyclotron resonance (FTICR), and liquid secondary ion mass spectrometry (LSIMS) show collectively that a mixture of polyhydrofullerenes, containing C60H18 through to C60H36 with a skewed distribution centred on C60H32 is formed, the discrepancy in results arising from the thermal lability of this mixture of polyhydrofullerenes when subjected to the elevated temperatures (>250 °C) required for mass spectroscopic studies using direct-insertion heated probes.

Aziridino[2′,3′ : 1,6][60]fullerene: isolation of the first closed [5,6]-bridged fullerene adduct

In addition to the expected formation of closed [6,6]-bridged azmdinofullerene 3 by reaction of [60]fullerene with singlet oxycarbonylnitrenes, small amounts (ca. 10%) of previously undetected closed [5,6]-adducts 5 have been isolated, and are thought to arise by trapping of triplet nitrenes.