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1.
Andrzej Barszczewicz Michal Jaszuński Krystyna Kamieńska-Trela Trygve Helgaker Poul Jørgensen Olav Vahtras 《Theoretical chemistry accounts》1993,87(1-2):19-28
Summary
Ab initio calculations of parameters which characterize the NMR spectrum are presented for the cyclopropene molecule. The London orbitals CHF (or GIAO-CHF, Gauge-Independent Atomic Orbital Coupled Hartree-Fock) results for the shielding constants are in good agreement with the experimental data, accurately determined, and with otherab initio values. The calculations of the NMR spin-spin coupling constants have been performed using the Multiconfiguration Time-Dependent Hartree-Fock (MC TDHF) approach. Different basis sets and MC SCF wavefunctions were used to estimate the accuracy of the results. Good agreement is obtained with the coupling constants estimated using the available experimental data.Dedicated to Professor Werner Kutzelnigg on the occasion of his 60th birthday 相似文献
2.
A general method is described for the resolution of cycloprop-2-ene carboxylic acids via diastereomeric N-acyloxazolidines prepared from enantiomerically pure oxazolidinones. Although a number of oxazolidinones were shown to resolve cyclopropene carboxylic acids, the oxazolidinones of S-phenylalaninol, S-phenylglycine and (1S,2R)-cis-1-amino-2-indanol are optimal in terms of resolving power and cost effectiveness. Separations were performed using simple flash chromatography, and because there is typically a large difference in Rf values it is possible to separate gram quantities of pure diastereomers in a single chromatogram. The cycloprop-2-ene carboxylic acids that can be resolved include those that are substituted at the 1-position by H, Ph, α-naphthyl, CO2Me, CH2OMOM, and trans-styryl; alkene substituents include Me, n-alkyl, Ph and tethered alkynes. Remarkably, 2-methyl-3-propylcycloprop-2-ene carboxylic acid can also be resolved with ease. The relative configurations of four diastereomerically pure oxazolidines were determined by X-ray crystallography. Reduction of the N-acyloxazolidinones with LiBH4 give enantiomerically pure derivatives of 3-hydroxymethylcyclopropene that react with either MeMgCl or vinylMgCl and catalytic CuI to give enantiomerically pure products of syn-addition. 相似文献
3.
Jessica K. Su Zexin Jin Rui Zhang Gang Lu Peng Liu Yan Xia 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(49):17935-17940
Ring‐opening metathesis polymerization (ROMP) has become one of the most important living polymerizations. Cyclopropenes (CPEs) remain underexplored for ROMP. Described here is that the simple swap of 1‐methyl to 1‐phenyl on 1‐(benzoyloxymethyl)CPEs elicited strikingly different modes of reactivity, switching from living polymerization to either selective single‐addition or living alternating ROMP. The distinct reactivity stems from differences in steric repulsions at the Ru alkylidene after CPE ring opening. Possible olefin or oxygen chelation from ring‐opened CPE substituents was also observed to significantly affect the rate of propagation. These results demonstrate the versatility of CPEs as a new class of monomers for ROMP, provide mechanistic insights for designing new monomers with rare single‐addition reactivity, and generate a new functionalizable alternating copolymer scaffold with controlled molecular weight and low dispersity. 相似文献
4.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(31):9335-9338
An enantioselective C−H addition to a C=C bond represents the most atom‐efficient route for the construction of chiral carbon–carbon skeletons, a central research topic in organic synthesis. We herein report the enantioselective yttrium‐catalyzed C(sp3)−H bond addition of 2‐methyl azaarenes, such as 2‐methyl pyridines, to various substituted cyclopropenes and norbornenes. This process efficiently afforded a new family of chiral pyridylmethyl‐functionalized cyclopropane and norbornane derivatives in high yields and high enantioselectivities (up to 97 % ee ). 相似文献
5.
An efficient and regioselective synthesis of polysubstituted benzene derivatives was achieved via multicomponent reaction of a substituted cyclopropenone acetal and two alkyne molecules. The synthesis utilizes cyclopentadienone acetal as an intermediate and enables regioselective [2+2+2] assembly of the three-components into a benzene ring. A variety of polysubstituted benzene derivatives of synthetic and structural interest have been synthesized. 相似文献
6.
7.
Haifeng Zheng Michael P. Doyle 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(36):12632-12636
A chiral copper(I) complex catalyzes reactions of symmetric diaziridines with enol diazo compounds, which react through N?N bond ring opening in a formal [3+3] cycloaddition to form four chiral centers with high stereocontrol. A broad spectrum of bridged dinitrogen heterocycles were obtained in high yields and excellent diastereo‐ and enantioselectivities from γ‐substituted enol diazoacetates, while their geometrical isomers gave different enantioselectivities. Donor–acceptor cyclopropenes formed from the geometrical isomers of the γ‐substituted enol diazoacetates underwent catalytic ring opening to give only the Z isomer of the metalloenolcarbene intermediate, provided excellent yields and selectivities for the 1,5‐diazabicyclo[n.3.1]non‐2‐ene derivatives. 相似文献
8.
Wilhelm Graf von der Schulenburg Henning Hopf Robin Walsh 《Angewandte Chemie (International ed. in English)》1999,38(8):1128-1130
The secret of the mechanism of vinylidene rearrangements has been unlocked by the use of specifically labeled cyclopropenes under mild thermal conditions (see the Equations). 13C labeling gives the surprising 1,2-alkyl migratory aptitude sequence Et>iPr>Me. Deuterium labeling yields the first measurement of the primary kinetic isotope effect in the ring opening of a cyclopropene to form a vinylidene. 相似文献
9.
Changkun Li 《Tetrahedron letters》2009,50(24):2956-901
AuPPh3Cl/AgOTf-catalyzed reaction of cyclopropenes is found to be highly efficient, giving indene derivatives in high yields. The reaction is suggested to proceed through gold vinyl carbenoid intermediate. 相似文献
10.
A convenient and inexpensive approach to the generation of 3-phenylcyclopropenes is described. Reaction of these compounds with a range of dienophiles and dipolarophiles led to the stereoselective formation of [4+2]- and [3+2]-cycloadducts, which were exclusively exo-3-phenyl-cis-1,2-disubstituted cyclopropanes. Efficient trapping of 1-lithio-3-phenylcyclopropene with different electrophiles is also discussed. Ab initio calculations suggest that the lowest energy conformation of 3-phenylcyclopropene has the plane of the benzene ring perpendicular to the cyclopropene π-bond but with a low rotation barrier. 相似文献