摘要:

AbstractThe present article deals with acid‐catalyzed rearrangements and thermal valence isomerizations in cyclobutenes. The characteristic features of small rings, i.e. their practically planar structure and the ring strain, are in fact the causes of the rearrangements discusse

ISSN:0570-0833    

DOI:10.1002/anie.196805591

出版商:Hüthig&Wepf Verlag    

年代:1968

数据来源: WILEY

摘要:

AbstractAccording to quantum mechanical calculations, systems with 4n π electrons ought to have anti‐aromatic character, i.e. be destabilized by resonance. This prediction is examined for the case of cyclopropenyl anion, the simplest system having 4n π electrons (n = 1). Isolation of compounds containing the cyclopropenyl anion has not, as yet, been achieved; however, kinetic measurements indicate the existence of the ion and confirm the unusual properties predic

ISSN:0570-0833    

DOI:10.1002/anie.196805651

出版商:Hüthig&Wepf Verlag    

年代:1968

数据来源: WILEY

摘要:

AbstractThere are three important direct routes to cyclopropylcarbonyl compounds: 1. Cyclization of chains of three carbon atoms, the first or third of which is adjacent to a carbonyl or potential carbonyl carbon atom (this type includes syntheses by intramolecular alkylation of γ‐halogeno ketones or related compounds in alkaline media); 2. insertion of a methylene group or substituted methylene group into the olefinic double bond of an α,β‐unsaturated carbonyl compound; and 3. introduction of an acetonyl group into the double bond of an olefin. However, cyclopropylcarbonyl compounds can also be obtained from 1,2‐epoxycyclobutane and 2‐bromocyclobutanone derivatives by ring contraction. Another possibility is the dehalogenation of α,α‐bis(bromomethyl) cycloalkanones. This review concludes with a discussion of these little known routes and of a particularly suitable method which involves the reaction of methylene iodide, a ZnCu couple, and α,β

ISSN:0570-0833    

DOI:10.1002/anie.196805701

出版商:Hüthig&Wepf Verlag    

年代:1968

数据来源: WILEY

摘要:

AbstractThis review article deals with the stereochemistry of the following ring opening reactions: 1. Homoallylic rearrangement of secondary and tertiary cyclopropyl alcohols in the presence of electrophilic reagents, 2. The addition of carboxylic acids to vinylcyclopropanes, 3. The thermal rearrangement of vinylcyclopropanes into cyclopentenes. An account is also given of the NMR spectroscopic determination of the conformations of substituted vinylcyclopropanes.

ISSN:0570-0833    

DOI:10.1002/anie.196805771

出版商:Hüthig&Wepf Verlag    

年代:1968

数据来源: WILEY

摘要:

AbstractThe reaction of chloromethyl phenyl ether with butyllithium in olefins yields phenoxy‐cyclopropanes. 1‐Chloro‐1‐phenoxycyclopropanes can be prepared in a similar manner, though the yields are poor. Alkoxycyclopropanes are formed when dichloromethyl alkyl ethers are treated with methyllithium/lithium iodide in the presence of olefins. Cyclopropanols can be obtained in good yields by reaction of (β‐chloroethoxy)cyclopropanes either with butyl‐ or ethyllithium or with bases. – As was shown by acetolysis experiments with cyclopropyl p‐toluenesulfonates having a known steric configuration, the rearrangement of a cyclopropyl derivative into an allyl cation proceeds in accordance with the Woodward‐Hoffmann‐DePuy rule. The solvolysis of exo‐bicyclo[n.1.0]alkyl p‐toluene‐sulfonates is assumed to proceed via “semi‐open” intermediates, which are somewhere between an allyl

ISSN:0570-0833    

DOI:10.1002/anie.196805881

出版商:Hüthig&Wepf Verlag    

年代:1968

数据来源: WILEY

摘要:

AbstractThe applications of adhesives have been greatly extended by the use of synthetic organic high polymers. It is possible nowadays to bond, not only wood, leather, and paper, but also glass, high‐strength plastics, and metals with adhesives of this type. They give satisfactory adhesion, flexibility, and mechanical properties even at high temperatures. A particularly important advance was the introduction of chemically or mechanically blocked polymer systems, which can reduce the cost of curing equipment when used as adhesive

ISSN:0570-0833    

DOI:10.1002/anie.196805981

出版商:Hüthig&Wepf Verlag    

年代:1968

数据来源: WILEY

摘要:

AbstractReactions belonging to the formal category of electrophilic substitutions at phosphorus are classified according to mechanism and the coordination number of the phosphorus atom.

ISSN:0570-0833    

DOI:10.1002/anie.196806061

出版商:Hüthig&Wepf Verlag    

年代:1968

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196806171

出版商:Hüthig&Wepf Verlag    

年代:1968

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196806181

出版商:Hüthig&Wepf Verlag    

年代:1968

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196806191

出版商:Hüthig&Wepf Verlag    

年代:1968

数据来源: WILEY