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de Meijere A

Publications and source records attributed to de Meijere A.

9 recordsLinked to original sources
PubMed2000

Facile preparation of Hexahydropyrrolo

Chlorolactames 2a-f reacted with sodium azide to give the cyclopropylketimines 3a-f (75-89%), and acid hydrolysis of 3c,d yielded the cyclopropylketones 6c,d (61-67%). Compounds 3a-f and 6c, d were transformed by heating (170-240 degrees C, sublimation) to the air-sensitive dihydropyrroles 4a-f (51-71%) and dihydrofurans 7c, d (85-91%). Oxidation of the dihydro derivatives 4a-f and 7c,d with DDQ led to novel types of pyrrolo[3,2-e][1,4]diazepinedione derivatives 5a-f (75-84%) and furo[1H][3,2-e][1,4]diazepinediones 8c, d (91-93%).

Journal Article↗
PubMed2000

Fischer Carbene Complexes as Chemical Multitalents: The Incredible Range of Products from Carbenepentacarbonylmetal alpha,beta-Unsaturated Complexes.

The metal carbene complexes, discovered by E. O. Fischer at the start of the 1960s and carrying his name, have since proved themselves to be irreplaceable building blocks for organic synthesis. In particular, since the discovery of the Dötz reaction, a formal cycloaddition of Fischer alpha,beta-unsaturated carbene complexes to alkynes with CO insertion, this area of chemistry has become increasingly interesting to organic chemists. In spite of the considerable diversity of reactions performed with these complexes, proper selection of substrates and careful adjustment of the reaction conditions have allowed, in most cases the perfectly selective preparation of individual compounds of this enormous range of products. The spectrum of new successes begins with the conventional Diels-Alder reaction of alkynylcarbene complexes and the formal regioselective [3+2] cycloaddition of alkenylcarbene complexes to alkynes. It extends much further, however, from cascade reactions with the formation of oligofunctional and oligocyclic products of impressive molecular complexity to complex, formal [3+6] cocyclizations in which six bonds are formed in a single operational step. Beyond doubt, the methodological arsenal of preparative organic chemistry cannot be imagined any more without the valuable transformations of the Fischer carbene complexes; it only remains to be seen whether one or other of the numerous new types of cocyclization products of these complexes can establish itself as a lead structure in the search for biologically active compounds.

Journal Article↗
PubMed1999

The First Enantiomerically Pure Triangulane (M)-Trispiro

A remarkably high specific rotation, even at 589 nm, is shown by (M)-1, the first enantiomerically pure unbranched [4]triangulane, although it has no chromophore that would lead to any significant absorption above 200 nm. This outstanding rotatory power is in line with a helical arrangement of its sigma bonds, as confirmed by high-level computations. Thus, it is appropriate to call (M)-1 a "sigma-[4]helicene", the first sigma-bond analogue of the aromatic [n]helicenes.

Journal Article↗
PubMed1999

Tricyclopropylamine and Its Radical Cation.

A surprisingly high first vertical ionization energy (8.44 eV) and an unusually high oxidation potential are exibited by tricyclopropylamine (1)-in sharp contrast to triisopropylamine. These are attributed to the near-tetrahedral geometry of 1 at the N atom and the perpendicular orientation-with respect to the N-orbital axis-of the cyclopropyl groups. gamma-Irradiation of 1 led to the radical cation 1(.)(+), which, in accord with computations, has a planar C(3h)-symmetrical structure. The EPR-spectroscopic and computational results disclose a dramatic, previously not reported, conformational change on going from 1 to 1(.)(+).

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