ALBERT

Notes: The structures of the norbornenyl and norbornyl sulfones exo-5, endo-5 and endo-6 have been determined experimentally, by X-ray analysis, and theoretically by ab initio calculations (HF/6-31+G*). X-ray crystal structure analyses of the lithiated allylic norbornenyl and norbornyl sulfones endo-3/ent-endo-3·2diglyme and endo-4/ent-endo-4·2diglyme revealed dimeric O-Li contact ion pairs devoid of C-Li bonds. The anions of endo-3/ent-endo-3·2diglyme and endo-4/ent-endo-4·2diglyme adopt both the endo conformation (C2-S) and are characterized by in the exo direction pyramidalized anionic C atoms. The degree of pyramidalization of the C2 atom of 3 is higher than that of 4. Ab initio optimizations (HF/6-31+G*) of the structures of the anions of methylenenorbornene I and methylenenorbornane II resulted in local minima featuring non-planar C2 atoms which are pyramidalized in the exo direction in both cases, but to different degrees. In both cases cryoscopy of 3 and 4 in THF at -108.5 °C revealed approximately 1:1 mixtures of monomers and dimers. The sulfones exo-5, endo-5, exo-6 and endo-6 as well as the lithiosulfones 3 and 4 were studied by NMR spectroscopy. 1H-NMR (400 MHz), 13C-NMR (100 MHz) and 6Li-NMR (44 MHz) spectroscopy of 3 and 4 at -100 °C in [D]8THF revealed in each case only one set of signals, independent of the configuration of the starting sulfones. This indicates in both cases that attainment of both the monomer-dimer and the endo/exo equilibria of 3 and 4 is fast on the NMR time scale. According to 6Li{1H}- and 1H{1H}-NOE experiments of 3 and 4 the monomeric and dimeric species endo-3 and endo-4, having endo anions, seem to be preferred in THF solution. Ab initio calculations of the anions of 3 and 4 resulted in structures endo-3(-Li+), exo-3(-Li+), endo-4(-Li+) and exo-4(-Li+) (HF/6-31+G*), whose atomic point charges were calculated by the method of Kollman et al. The C2 atoms of endo-3(-Li+) and endo-4(-Li+) are pyramidalized in the exo direction whereas the C2 atoms of exo-3(-Li+) and exo-4(-Li+) are pyramidalized in the endo direction. According to the calculations, the endo anions are more stable than the exo anions. There is good agreement between the optimized structures of the free anions and the experimentally determined structures of the anions of the contact ion pairs in the crystal. Reactions of 3 and 4 with DX, MeI, EtI, nPrI and nHeI occurred at the C2 atom under the selective formation of the corresponding endosulfones endo-8a-e and endo-9a-e, respectively, in all cases. Thus, an earlier report on the selective formation of the exosulfone exo-9b in the reaction of 4 with MeI has to be revised. Product ratios were independent of the configuration of the starting sulfones and varied with the nature of the electrophile. Selectivities were highest in the case of the norbornyl species 4. Reaction of 3 with PhCHO occurred at the α position (C2) to afford the alcohols endo-8f and exo-8f (88:12) as single diastereomers and at higher temperatures at the γ position (C8), whereas reaction of 4 with PhCHO took place at the γ position even at low temperatures. Methylation of endo-5 and exo-5 at -105 °C by both the stepwise method and by the in situ method gave different ratios of exo- and endo-methylation products. The selectivities of reaction of 3 and 4 with electrophiles have been rationalized by the Curtin-Hammett/Winstein-Holness concepts. It is proposed that endo-3 (endo-4) and exo-3 (exo-4) are conformationally labile on the time scale defined by the rate of their reactions with electrophiles, and are attacked by electrophiles with high selectivities from the exo and the endo face, respectively, because of the shielding by the phenyl group and the direction of the pyramidalization of the anionic C atom. Preferential formation of the endosulfones is thus ascribed to exo attack of electrophiles on endo-3 (endo-4) being faster than endo attack on exo-3 (exo-4) because of Houk's staggering effect. Methylation of 3 and 4 by the in situ method showed 3, whose C2 atom is stronger pyramidalized, to be more reactive than 4. The base-catalyzed H/D exchange of sulfones endo-5, exo-5, endo-6 and exo-6 with NaOCD3 in CD3OD proceeded in all cases with a high degree of retention of configuration.

Notes: No abstract

Notes: 16-Electron complexes of zerovalent nickel with diallylamines, Ni[(C3H5)2NR]L [1, 2: L = P(CH3)3, R = CH3, C6H5; 3: L = P(C6H5)3, R = CH3] and [NiP(CH3)3]2CH2[N(C3H5)2]2 (4), were synthesized by reduction of NiCl2L2 with magnesium in tetrahydrofuran. NiCl(η3-C3H5)[P(CH3)3]2 (5), a low-yield byproduct, was also obtained in high yield from NiL4 and C3H5Cl. With triallylamine as starting material complexes Ni[(C3H5)3N]L [6: L = P(CH3)3; 7: L = P(C6H5)3] were generated exhibiting η6- and η4-olefin coordination, respectively. 17-electron cobalt(O) compounds Co[(C3H5)2NR](PMe3)2 (8, 9: R = CH3, C6H5) were obtained by reaction of Co(cyclo-C5H8)(PMe3)3 with the corresponding diallylamine, while CoR(PMe3)4 (R = CH3, C6H5) reacted with N,N-diallylaniline to give diagmagnetic Co[(η3-C3H4)(η2-C3H5)NC6H5](PMe3)2, (10). The coordination mode of allylic functions was deduced from IR, ESR and especially 1H- and 13C-NMR spectra including 2D-NMR experiments.

Notes: It is shown by NMR spectroscopic arguments, including twodimensional 13C INADEQUATE experiments, that the adducts of the diazocyclopentadienes 1a and 1b with dimethyl acetylenedicarboxylate have the 3H-indazole structure 3 and not, as was reported in the case of 1b, the spirononatetraene structure 2.

Notes: Eine ausgefeilte Synthese der homochiralen Bausteine 2a und ent-2a mittels der „Enantiotopos-Enzym-Konzeption“ für die enantioselektive Totalsynthese von Cyclopentanoiden wird beschrieben. Deren Schlüsselschritte sind die nahezu quantitative, PLE-katalysierte asymmetrische Verseifung des meso-Diesters 8 zum homochiralen Halbester 9, dessen Absolutkonfiguration durch Röntgenstruktur-Analyse des (-)-Ephedrinsalzes 12 bestimmt wurde; die Gewinnung von optisch reinem 9 und ent-9 durch Racematspaltung von rac-9 mit (+)- und (-)-Ephedrin; die enantiodivergente Synthese der Lactone 18 und ent-18 aus 9 sowie die enantiokonvergente Synthese von 18 oder ent-18 aus 9 sowie die enantiokonvergente Synthese von 18 oder ent-18 aus 9 und ent-9 durch wahlweise chemoselektive Reduktion der Ester- und Carboxygruppe und schließlich die regioselektive Dieckmann-Cyclisierung der isomeren Diester 23b/24b bzw. ent-23b/ent-24b zu den cyclopentanoiden Zielverbindungen 2a und ent-2a. Die Strukturen von 23b, 24b, rac-2b und rac-29 wurden durch INADEQUATE-13C-NMR-Experimente bestimmt. Dieckmann-Cyclisierung des trans-Diesters rac-31 führt ebenfalls zu rac-2a und rac-26a.