Malcolm R. Banks

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.

Synthesis of enantiomerically pure (5S)-4-aza-2-oxa-6,6-dimethyl-7,10-methylene-5-spiro[4.5]decan-3-one, a novel chiral oxazolidin-2-one from (-)-camphene for use as a recyclable chiral auxiliary in asymmetric transformations

By an intramolecular nitreno-mediated route (-)-camphene is transformed into a novel spiro-oxazolidin-2-one whose efficiency as a chiral auxiliary is highlighted by the excellent levels of chiral induction attained in an array of asymmetric transformations such as the Diels-Alder, conjugate addition, aldol condensation, alkylation and acylation reactions