The One-Electron Reduction of Carbonium Ions. V. A Kinetic Study on the Reduction of the Substituted Cyclopropenium Ions with Cr(II)
作者:Kunio Okamoto、Koichi Komatsu、Akira Hitomi
DOI:10.1246/bcsj.46.3881
日期:1973.12
cyclopropenium ions with Cr(II) has been carried out in a 10% HCl solution. The reduction of triphenylcyclopropenium (Ia), diphenyl-n-propylcyclopropenium (Ib), and phenyldi-n-propylcyclopropenium (Ic) ions quantitatively gives dimers of the respective cyclopropenyl radicals, i.e., the bis(cyclopropenyl) derivatives, whereas the tri-n-propylcyclopropenium ion (Id) is quite unreactive. A kinetic study has shown
Metal-Catalyzed Cyclopropene Rearrangements for Benzannulation: Evaluation of an Anthraquinone Synthesis Pathway and Reevaluation of the Parallel Approach via Carbene-Chromium Complexes
作者:M. F. Semmelhack、Suzzy Ho、D. Cohen、M. Steigerwald、M. C. Lee、G. Lee、Adam M. Gilbert、William D. Wulff、Richard G. Ball
DOI:10.1021/ja00095a014
日期:1994.8
The reaction of 3-arylcyclopropenes with Cr(CO)(6) and Mo(CO)(6) produces naphthols, in an example of metal-promoted benzannulation. Substituents at C-3 (in addition to aryl) have a strong effect on the success of the process: 3-H derivatives are generally effective, but the yields decrease for 3-alkyl derivatives as the size of the alkyl group increases. The 3,3-diphenyl and 3-cyano derivatives are unreactive. The mechanism is postulated to involve metal-complexed vinyl carbene units, parallel with the benzannulation reaction involving arylcarbene complexes with alkynes. The regioselectivity has been probed with various unsymmetrically 1,2-disubstituted 3-arylcyclopropenes. The results suggest a simple correlation with steric size, consistent with initial cleavage of the cyclopropene sigma bond bearing the smaller substituent. The result of this regioselectivity is a product structure showing a substituent arrangement opposite to that from the carbene-chromium approach; the smaller substituent of the cyclopropyl double bond ends up adjacent to the phenol OH in the product. Catalytic activity at low efficiency was observed, using a Mo(CO)a catalyst. However, the use of Mo(CO)(6) also promotes formation of indenes as significant byproducts at the expense of naphthalenes. Attempts to use the arylcyclopropene rearrangement to convert a 3-(1,4-dimethoxy-2-naphthyl)cyclopropene to an anthraquinone skeleton produced instead a phenanthrene via an unusual substitution for a methoxy substituent. A related example previously reported to produce anthraquinones via the naphthylcarbene-chromium/ alkyne reaction was shown to be in error; the correct structure is again a phenanthrone, and the product is exactly parallel with that observed in the cyclopropene rearrangement. A naphthoquinone substituted with a cyclopropene at C-2 does provide the first example of metal-promoted benzannulation to give an anthraquinone.
THE SYNTHESIS OF BIS-TRIPHENYLCYCLOPROPENYL, AN UNDISSOCIATED DIMER OF THE TRIPHENYLCYCLOPROPENYL RADICAL, AND ITS ISOMERIZATION TO HEXAPHENYLBENZENE
作者:Ronald Breslow、Peter Gal
DOI:10.1021/ja01526a077
日期:1959.9
Isomerization of Biscyclopropenyls to Benzenes<sup>1,2</sup>
作者:Ronald Breslow、Peter Gal、Hai Won Chang、L. J. Altman
DOI:10.1021/ja00950a028
日期:1965.11
Gompper,R. et al., Chemische Berichte, 1979, vol. 112, p. 218 - 233