Cyclopropane, cyclopropylidene

Data for substituted cyclopropane rings can be conveniently arranged in five categories substituted cyclopropane sets, cyclopropylidene sets, trans-cyc o-propylene sets, cis-cyclopropylene sets, and reactions of cyclopropane rings. The correlation of data for cyclopropanes with the Hammett equation (19) and the extended Hammett equation (215) has been reported by Charton. 

Transition metals 172 a-bonded to cyclopropanes, substituted on the a-carbon with a halogen atom, are interesting intermediates for cyclopropylidene complexes 173 or allene ones 174 [88]. The former complexes are also supposed to be precursors of the above-mentioned nickel enolates. (Scheme 65)... 

The GIAO-MP2/TZP calculated 13C NMR chemical shifts of the cyclopropylidene substituted dienyl cation 27 show for almost all carbon positions larger deviations from the experimental shifts than the other cations 22-26. The GIAO-MP2/TZP method overestimates the influence of cr-delocalization of the positive charge into the cyclopropane subunit on the chemical shifts. Electron correlation corrections for cyclopropylidenemethyl cations such as 27 and 28 are too large to be adequately described by the GIAO-MP2 perturbation theory method and higher hierarchies of approximations such as coupled cluster models are required to rectify the problem. 

The 3 + 2-cycloaddition of pyrroline A-oxide to 2-chloro-2-cyclopropylidene acetate and its spiropentane analogues (60) yields spiro [cyclopropane-1,5 -isoxazolidinejs (61) which undergo a novel cascade ring enlargement to yield indolizinones (62) in high yield (Scheme 21). ... 

Commonly known methods for the preparation of bkyclopropylidenes of types 55-62 (Fig. 3) are the cyclopropanations of appropriately cyclopropanated al-lenes according to the Gaspar-Roth [60] or modified Simmons-Smith protocol [61] or addition of cyclopropylidene generated in situ from AT-nitroso-N-cyclo-propylurea [62,63]). Along these routes, the compounds 55 [63], 58-60 [33,64, 65], and 62 [33,64] were obtained in low to moderate yields (Scheme 11). 

Das ziemlich einfach herstellbare 1 -Hydroxy- 1-piperidino-cyclopropan kann in Gegen-wart von Titan(IV)-chlorid in einer Variante der Mannich-Reaktion als Aquivalent von Cyclopropanon/Piperidin dienen nach der anzunehmenden in-situ-Umwandlung in 1-Cyclopropyliden-piperidinium-chlorid erfolgen Reaktionen z.B. mit 1-Trimethylsiloxy-cyclohexen zu 2-Oxo-l-(l-piperidino-cyclopropyl)-cyclohexan (63%) und mit 1-Methyl-pyrrol bzw. Indol zu l-Methyl-2-( 1-piperidino-cyclopropyl)-pyrrol (65%) bzw. 3-(l-Pipe-ridino-cyclopropyl)-indol (84%)2 ... 

Unusual bridging (//-cyclopropyIidene)diiron complexes having a tetrahedral carbene carbon have been studied as model intermediates in carbon-carbon bond formation in the Fischer-Tropsch synthesis248. The cyclopropylidene complexes cis- and trans-[Cp(Co)Fe]2(/(-Co)(//-C,H4) were readily prepared by cyclopropanation in ether, of the corresponding cis- and mww-vinylidene complexes [CpCoFe](//-CO)(//-CH2) with diazomethane in the presence of CuCl (equation 181). Both isomers are air stable in the solid state. Solutions of the complexes are air stable for several hours, provided they are kept in the dark. The pure //-cyclopropylidene isomers slowly interconvert in solution, like their parent /z-vinylidene and other alkylidene complexes. The final equilibrium ratio cis .trans = 4.8 1 is reached after two weeks. 

Cyclohexan (Cyclopropyliden-methylen)- E17b, 1493 (Br2—cyclopropan -> Allen) Cyclopropan... 

Isopropyliden-l-(2-methyl-propen-yliden)-E19b, 144 (Carben + En) Cyclopropan-(spiro-3)-bicyclo 2.2.0 hexan-<2-spiro>-cyclopropan E17c. 2236 (Cyclobuten + Bi-cyclopropyliden) Cyclopropan--bicyclo 2.2.2 oct-2-en El7b, 1531 (1,3-Cyclo-hexadien + En)... 

Cyclobutan l-Hydroxymethyl-2-oxo-1-phenyl- E17e, 186/266 (2-Ar— 2-cyclopropyliden-ethano /TiX4/R—O — OH) Cyclopentan--l,3-benzodixol El4a/1, 64 (Umacetalisier.) Cyclopropan... 

Cyclopropan-[Pg.1030]

Cyclohexan 4-tert,-Butyl-l-cyclopropyliden- E17b, 1496 ( —R3Si —OH - En) Cyclopropan 3-Cyclohexyliden-c/.s-2-isopropyl-l-methyl- E19b, 116 (Carben + En)... 

This is the other possible cyclic isomer of C3H4 and may be considered as a cyclic carbene. Only the singlet state has been considered, although it is possible that an associated triplet state may be lower in energy. C v symmetry was assumed in the structure determination. The cyclopropylidene skeleton is rather similar to that of cyclopropane, from which... 

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