Michael R. J. Dorrity

Palladium-catalysed polycyclisation-anion capture processes

Abstract Aryl iodides containing appropriately located 1, n-diene, -diyne, and -enyne moieties undergo palladium catalysed bis-cyclisation with anion capture (H − , Ph − ) apart from the 1, n-enyne which undergoes a tri-cyclisation without anion capture. The reactions lead to the regio- and stereo-specific creation of ring junction-, spiro- and remote ring-tetrasubstituted carbon centres.

X=Y-ZH systems as potential 1,3-dipoles. Part 34. generation of nitrones from oximes. Tandem michael addition-1,3-dipolar cycloaddition reactions. class 2 processes utilising bifunctional michael acceptor-dipolarophile components. ☆ ☆☆

Aldoximes and ketoximes react with a range of bifunctional Michael acceptor-dipolarophile substrates comprising functionalised 1,3-, 1,4- and 1,5-dienes via a tandem process involving an N-alkenyl nitrone intermediate. The 1,3-dienes react regio- and stereo-specifically to give 1-aza-7-oxabicyclo[2.2.1]heptanes whilst sterically unencumbered aryl aldoximes and 1,4-dienes give 1-aza-2-oxabicyclo[3.2.1]octane derivatives. Ketoximes and 1.4-dienesgive mixtures of 1-aza-2-oxa- and 1-aza-8-oxa-bicyclo[3.2.1]octanes. 1,5-Dienes and ketoximes react regio-and stereo-specifically to give 1-aza-8-oxabicyclo[3.2.1]octane derivatives whilst benzaldoxime gives a 1:1 mixture of epimeric 1-aza-8-oxabicyclo[3.2.1]octanes together with traces of two epimeric 1-aza-2-oxabicyclo[3.2.1]octanes. The regio- and stereo-chemical outcome of the tandem process is controlled by the length and nature of the linking chain in the bifunctional substrate and the steric interactions between substituents on the oxime and dipolarophile in the transition state. A crystal structure of one of the 1-aza-7-oxabicyclo[2.2.1]heptanes is reported.

X=Y−ZH compounds as potential 1,3-dipoles. Part 43. Metal ion catalysed asymmetric 1,3-dipolar cycloaddition reactions of imines and menthyl acrylate☆

Abstract Metallo-azomethine ylides, generated from imines by the action of amine bases in combination with LiBr or AgOAc, undergo cycloaddition with both 1R, 2S, 5R- and 1S, 2R, 5S-menthyl acrylate at room temperature to give homochiral pyrrolidines in excellent yield. The stronger the base the faster the cycloaddition and the greater the yield with: 2- 2-t-butyl-1,1,3,3-tetramethylguanidine > DBU > NEt 3 . X-Ray crystal structures of representative cycloadducts establish that the absolute configuration of the newly established pyrrolidine stereocentres is independent of the metal salt and the size of the pyrrolidineC(2)-substituent for a series of aryl and aliphatic imines.

Metal ion catalysed asymmetric 1,3-dipolar cycloaddition reactions of imines of α-amino esters

Abstract Cycloaddition of a range of imines of α-amino esters to homochiral menthyl acrylate proceeds with complete asymmetric induction at room temperature in the presence of silver(I), lithium(I) and thallium(I) salts. The imine of 2-aminomethylpyridine reacts similarly. Reversal of cycloaddition regiochemistry, together with complete asymmetric induction, occurs when titanium (IV) complexes are used as catalysts. The absolute configuration of one of the cycloadducts has been established by X-ray crystallography.

The Pd(0)-catalysed coupling reactions of 2-(tri-n-butylstannyl)-3,4-dihydrofuran and -5,6-dihydropyran.

The palladium(0) catalysed reaction of dihydropyranyl and dihydrofuranylstannanes offers an attractive route to the sythesis of 2-vinylhydropyrans and -furans.

X = Y-ZH systems as potential 1,3-dipoles. part 27 Intramolecular cycloaddition reactions of imines of cyclic secondary α-amino esters. dipole and cycloaddition stereochemistry

Abstract Condensation of cyclic secondary α- amino esters with aryl aldehydes containing an ω-alkenyl group leads to intramolecular 1,3-dipolar cycloaddition, via an intermediate azomethine ylide, in good yield. The stereochemistry of the azomethine ylides is controlled by steric interactions developing during conversion of the intermediate carbinolamines to the iminium ion species and generally results in stereo specific dipole formation. There is no pronounced endo - exo selectivity in these cycloadditions and an intramolecular β-acrylate moiety is a more reactive dipolarophile than an intermolecular maleimide moiety.

Regio- and stereo-specific class 2 tandem Michael addition−cycloaddition reactions of oximes

Abstract Oximes react regio- and stereo-specifically with 1,3-, 1,4- and 1,5-dienes bearing electronegative substituents via a tandem Michael addition-1,3-dipolar cycloaddition process to give bridged ring cycloadducts in good yield.

Structure and stereochemistry of cis-dihydro diol and phenol metabolites of bicyclic azaarenes from Pseudomonas putida UV4

Biotransformation of quinoline, isoquinoline, quinoxaline and quinazoline using growing cultures of Pseudomonas putida UV4 yielded cis-dihydro diols from the oxidation of the carbocyclic aromatic ring. Aromatic hydroxylation was observed in both carbocyclic and heterocyclic rings. Ring cleavage of the quinoline skeleton to yield anthranilic acid, and cis-diol formation (with alkene bond reduction) to yield cis-5, 6, 7, 8-tetrahydroquinazoline-5, 6-diol from quinazoline were observed. The cis-dihydro diol metabolites of quinoline (5, 6- and 7, 8-) and quinoxaline (5, 6-) were found to be optically pure, while metabolism of isoquinoline gave one homochiral (5, 6-) and one racemic (7, 8-)cis-dihydro diol product. The absolute configurations of the cis-dihydro diol metabolites have been determined using 1H NMR analyses, stereochemical correlations and X-ray crystallography methods.

X=Y-ZH Systems as potential 1,3-dipoles: Part 18. Cycloaddition of 4π-sulphinylaminomethamide species generated from α-amino acids and α-amino acid esters by sulphonyl group transfer. X-

Abstract Sulphonyl group transfer from N-sulphonyl aniline to α-amino acids followed by decarboxylation affords 4π-sulphinylaminomethamide species with an anti-configuration stereospecifically. Analogous reactions with α -amino acid etters occur at room temperature in toluene and afford carbomethoxy substituted 4π-sulphinylaminomethamide species non-stereoselectively. Both types of 4π-species are trapped in good yield in [3+2]-cycloaddition reactions by N-methylmaleimide. The mechanism of the reactions are discussed and evidence presented in favour of a 4π anionic species for the reactions involving α-amino acid esters. A novel cyclic intermediate is invoked to account for the stereospecific formation of anti-4π-sulphinylaminomethamide species from α-amino acids. These latter processes also probably involve 4π-anionic species.

THE REACTION OF C5H5Co(CO)2 WITH MeO2CC[tbnd]CCO2Me IN THE PRESENCE OF ELEMENTAL SELENIUM: MOLECULAR STRUCTURE OF 2,3,4,5,- TETRAKIS (METHOXYCARBONYL) SELENOPHENE

Abstract Cyclopentadienyldicarbonylcobalt reacts with dimethylacetylene dicarboxylate in the presence of selenium to yield cyclopentadienyl[1,2-bis(methoxycarbonyl)-1,2-diselenolato]cobalt (1), cyclopentadienyl[1-cyclopentadienyl-2,3,4,5-tetrakis(methoxycarbonyl)cobaltacyclopenta-2,4-diene]cobalt (2) and tetrakis(methoxycarbonyl)selenophene (3). These compounds have been characterized by spectroscopic and analytical techniques, and in the case of 3, by a single crystal X-ray diffraction study.