摘要:

AbstractThe addition of chlorosulfonyl isocyanate (CSI) to 6‐substituted benzonorbornadienes gives pairs of isomericsynandantiβ‐lactam products. Previously published molecular orbital calculations indicate that the benzonorbornadiene π‐bond is not polarized. Relative rate data are inconsistent with either a concerted addition process or a process which proceeds by the direct formation of a carbenium ion intermediate. A mechanism proceeding through the initial formation of a benzonorbornadiene‐CSI π‐complex which decays to a carbenium ion in a product determining step

ISSN:0021-2148    

DOI:10.1002/ijch.198100034

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractThis is a review of the pertinent literature on the subject of the stereochemistry of homolytic nonconcerted ring opening of small carbocycles. The data suggests that cyclopropane opens either without bond rotation or with a single rotation or with disrotatory double rotation; conrotatory double rotation has not yet been observed. Cyclobutane and cyclopentane undergo conrotatory ring opening that is coupled with another rotation to cause shearing of the bond to give a gauche 1,4‐ or 1, 5‐biradical. These biradicals apparently undergo bond formation with rearrangement via a least motion stereochemical pathway competitive with rotation around bonds to randomize the stereochemistry of the initially generated biradi

ISSN:0021-2148    

DOI:10.1002/ijch.198100035

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractThe syntheses and thermal rearrangements and/or fragmentations of 1,1‐difluorospiropentane,6, 1,1,4,4‐ and 1,1,2,2‐tetrafluorospiropentanes,7and8, 1,1,2,2,4,4‐hexafluorospiropentane,9, and perfluorospiropentane,10, are described., Spiropentanes6and7undergo only rearrangement to 2,2‐difluoromethylene‐cyclobutane and 1‐(difluoromethylene)cyclobutane and to 2,2,4,4‐tetrafluoromethylenecyclobutane, respectively. Spiropentanes8and9rearrange and extrude CF2: competitively, while perfluorospiropentane extrudes CF2: exclusively. Activation parameters are presented for all processes and the mechanisms of these thermal processes are disc

ISSN:0021-2148    

DOI:10.1002/ijch.198100036

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractRigid cyclopropyl ketones were rearranged by phosphorus pentachloride to furans. This ring‐expansion was also possible using bromine and an acid. A β, γ‐unsaturated ketone, a supposed intermediate in the reaction, gave furan products when treated with bromine

ISSN:0021-2148    

DOI:10.1002/ijch.198100037

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractIn 1‐vinyl substituted cyclopropanes hydrogenation with Pd/C leads mainly to simultaneous saturation of the side chain and specific ring opening at the adjacent C(1)‐C(2) bond. 1,4‐Addition of hydrogen is indicated by the detection of olefinic intermed

ISSN:0021-2148    

DOI:10.1002/ijch.198100038

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractThe effect of strain in determining the rate, mode and direction of singlet oxygen attack is explored using small ring olefins as substrates. The data suggests that1O2is relatively insensitive to strain considerations present in either the starting material or the product. More important factors seem to be the ground state geometry of the olefin, the interatomic distance between the α‐olefinic carbon and the γ‐allylic hydrogen, and the ionization potential of the double bond. Strain does, however, play a crucial and fascinating role in the secondary rearrangements of the primary1O2pro

ISSN:0021-2148    

DOI:10.1002/ijch.198100039

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractTransition metal organometallic complexes effect a wide range of useful and interesting cleavage reactions of three‐membered ring compounds. This review examines some recent developments in the organometallic chemistry of cyclopropanes, epoxides, episulfides and azirines. Novel synthetic approaches to heterocyclic [e.g., β γ and δ‐lactones, β‐lactams, isoxazoles, pyrazoles, indoles] and acyclic compounds [β‐diketones, vinyl isocyanates]have been achieved by means of these cleava

ISSN:0021-2148    

DOI:10.1002/ijch.198100040

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractThe reaction of (I)‐1‐fluoro‐1‐methyl‐2,2‐diphenylcyclopropane (1) with lithium metal produced a variety of ring‐opened, as well as cyclopropane, products. Initial electron transfer from the lithium metal surface to1is to the phenyl ring of1rather than to the carbon‐fluorine bond. Using chiral1, the 1‐lithio‐1‐methyl‐2,2‐diphenylcyclopropane produced yielded, upon carbonation, the corresponding acid which was largely racemized. The mechanism of the electron trans

ISSN:0021-2148    

DOI:10.1002/ijch.198100041

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractStarting from 1,2,4,5,6‐pentamethyl‐3‐methylenetricyclo[3.1.0.02.6]‐ hexane (3), a number of functionalized ethano‐bridged bicyclobutanes have been prepared. Ozonolysis of the carbon‐carbon double bond of compound3leads to the strained and sterically hindered ketone4which can be further transformed into tricyclic alcohols and azines. The formation of the rearranged lactone19in the oxidation of ketone4with O3or peracid is in agreement with a mechanism in which the 1,2‐alkyl shift from carbon to oxygen occurs by way of a β‐fission followed by a recombination step. Treatment of the dichlorocarbene adduct of alkene3with n‐BuLi afforded allene7, which on reaction with TCNE yielded a di‐ci

ISSN:0021-2148    

DOI:10.1002/ijch.198100042

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractThe reactions of alcohol1with HF‐SbF5and of alcohol8with FSO3H‐SbF5at low temperatures afforded dications [(CCH3)7H]2⊕and [(CCH3)7CH3]2⊕, respectively. Both NMR (1H and13C) data and analysis of the products, obtained upon quenching of the cations, were used to discuss the possible structures of these cations. Both ions showed a remarkable NMR behaviour, viz. an equivalency of all methylgroups on the one hand and all skeleton carbon atoms on the other hand, indicating a high symmetry or a rapid (on the NMR time scale) process. Using model compounds the weighted average13C‐NMR chemical shifts of reasonable structures for the ions were calculated and compared with the experimentally obtained values. The conclusion is drawn that the former reaction presumably leads to dications34and36and the latter reaction to d

ISSN:0021-2148    

DOI:10.1002/ijch.198100043

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY