Michael E. Stubbs

Base catalysed decomposition of oxaziridines to yield N-unsubstituted aldimines

Abstract A range of oxaziridines bearing an α-hydrogen atom on the N-alkyl substituent react with tertiary amines at ambient temperature to yield N-unsubstituted aldimines.

Formal synthesis of (±)-perhydrohistrionicotoxin

Abstract The syntheses of 1-benzyl-7-butyl-1-azaspirocyclo[5.5]undec-7-ene (14) [a formal precursor of perhydrohistrionicotoxin (2)] and the thermodynamically preferred, exocyclic isomer (13) in six steps from the readily available N -benzyloxycarbonyl-10-amino-Δ 1,9 -octalin (5) are reported.

The synthesis of NH aldimines and derivatives by spontaneous and base-catalysed decomposition of oxaziridines

A range of oxaziridines containing N-methylene substituents has been synthesized by peracid oxidation of the corresponding fluorenylidene N-alkylamines. Spontaneous and tertiary amine base-catalysed decomposition of the oxaziridines into unstable NH aldimines and derivatives was observed. Acrylaldehyde, 2-methylacrylaldehyde, and benzaldehyde NH imines have been identified as initial products from decomposition of the corresponding oxaziridines. 2,4,6-Trialkylhexahydro-1,3,5-triazines, N,N′-dialkylidene-1,1 -diaminoalkanes, N,N′-diarylidene-1,1 -diaminoalkanes, and N-iso-butylidene-2-methylpropenylamine were among the isolated products formed via the undetected alkyl aldehyde NH imines resulting from oxaziridine decomposition.

Racemization of phenanthrene 3,4-oxide. Absolute stereochemistry of cis- and trans-phenanthrene 3,4-dihydrodiols

trans-3,4-Dihydroxy-1,2,3,4-tetrahydrophenanthrene (11) and cis-3,4-dihydroxy-1,2,3,4-tetrahydrophenanthrene (12) have been prepared in optically pure form via: (i) chromatographic separation of the trans-3-bromo-4-menthyloxyacetoxy-1,2,3,4-tetrahydrophenanthrene diastereoisomers (7a), (7b), (ii) conversion of (7a) into the optically pure (+)-tetrahydro-3,4-epoxide (8), (iii)acid-catalysed hydrolysis of (+)-(8) by attack at C-4 to yield (+)-trans-(11) and (–)-cis-(12). Several lines of evidence, including spectral methods and chemical transformation to compounds of known absolute stereochemistry, have been used to assign absolute stereochemistry to all chiral compounds described in the present study. The availability of optically pure diols (11) and (12) has allowed the absolute stereochemistry of the trans- and cis-3,4-dihydrodiol metabolites of phenanthrene (4) and (2) to be determined as (–)-(3R,4R) and (+)-(3S,4R) respectively. Phenantherene 3,4-oxide, an initial mammalian metabolite of phenanthrene prepared from optically pure precursors, was optically active but racemized spontaneously at ambient temperature.

PROXIMITY EFFECTS IN 1‐AZASPIROCYCLO(5.5)UNDECANES. X‐RAY STRUCTURE DETERMINATION OF A DIOL DERIVATIVE

Das Olefin (II) last sich nicht zu (I) epoxidieren, jedoch kann das Brom-acetoxy-Derivat (III) mit NBS und Essigsaure erhalten werden.

An extremely mild acetate pyrolysis reaction. Novel synthesis and X-ray structure determination of 1-azaspiro[5.5]undecane derivatives

The azaspiro oxo-urethane (4), readily available from naphthalene, is reduced to the amino-alcohol (5) whose diacetate (6), the structure of which was determined by X-ray crystallography, undergoes acetate elimination in refluxing toluene to yield the N-acetylazaspiroundecene (7).

Thermal elimination reactions of nitrones. Part 2. A mechanistic study based on substituent and solvent effects

The rates of thermal elimination of isobutene from a series of N-(diarylmethylene)-t-butylamine N-oxides have been measured by u.v. spectroscopy. Activation parameters derived for N-(fluoren-9-ylidene)-t-butylamine N-oxide in decalin and t-butyl alcohol solvents are consistent with an intramolecular concerted mechanism involving a highly ordered cyclic transition state. Kinetic results from the thermal elimination of para-substituted N-(diarylmethylene)-t-butylamine N-oxides in protic and aprotic solvents however suggest that the reaction proceeds via a non-synchronous concerted mechanism in contrast to the Cope elimination of tertiary amine oxides.

Chemical resolution and racemization of 1,2- and 3,4-epoxydihydrophenanthrene

1,2- and 3,4-Epoxy-1,2,3,4-tetrahydrophenanthrene were each separable into enantiomers while the corresponding 1,2- and 3,4-epoxydihydrophenanthrene (derived from identical chiral precursors) showed evidence of spontaneous racemization; preliminary PMO calculations indicate that oxepin intermediates could account for this configurational instability.