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Carbocycles four-member

Carbocyclic four-membered rings 2, 4 and 5 were formed in good yields on treatment of the a,diethyl ether.7 Interestingly, the corresponding dibromides did not undergo clean intramolecular cyclization under the same conditions.7... [Pg.60]

Lately a third type of transition state has been favored for [2 + 2] cycloadditions forming carbocyclic and heterocyclic four-membered rings. The experimental data on the addition of diarylketenes to arylethylenes are well accommodated by the [ 2s + 2s + 2s] process proposed by Baldwin (70JA4874). The steric effects on the cycloaddition of allenes to ketenes also favor this mechanism (76JA7698). [Pg.39]

The palladium-catalyzed stannylboration (90) [124] or silylboration (87) [109, 114] succeeds in the intramolecular carbocyclization of diynes and enynes (Scheme 1-27). It is interesting that a very strained four-membered cycUzation of hexa-l,5-diyne proceeds without any difficulties, similarly to five- or six-membered cycUzation. The boryl group is selectively introduced into the more reactive C=CH rather than C=C for enynes and into the terminal C=CH rather than the internal C=CR for diynes, again suggesting a mechanism proceeding through the first insertion into the Pd-B bond in preference to the Pd-Sn or Pd-Si bond. [Pg.27]

The past 30 years have seen the development of a broad spectrum of widely applicable preparative methods for three- and four-membered carbocycles and the accumulation of detailed knowledge about their structure-reactivity relationships. Nowadays, more and more synthetic methodology is being developed, which utilizes the potential of small ring compounds as reactive entities. Cyclopropyl and cyclobutyl moieties in a molecule can be regarded as unique functional groups they allow transformations which are far more difficult or impossible with any of the more conventional functional groups. [Pg.5]

Hudlicky T, Reed JW (1991) Rearrangements of vinyl cyclopropane and related systems. In Trost BM (ed) Comprehensive organic synthesis, vol 5. Pergamon Press, Oxford, p 899 Hudlicky T, Becker DA, Fan RL, Kozhushkov S (1997) Carbocyclic three-and four-member-ed ring compounds. In de Meijere A (ed) Houben-Weyl methods of organic chemistry, vol El7c. Thieme, Stuttgart, p 2538... [Pg.87]

From Four-membered Rings 2.08.3.2.1 Carbocyclic rings... [Pg.485]

Photochemical reactions of quinones with allenes have also been studied and in some cases cyclobutane formation occurs, although in competition with products derived from attack of the allene on the carbonyl oxygen. Thus, photocycloaddition of tetramethyl-l,4-benzoquinone with 1,1-dimethylallene affords the four-membered carbocycle 6 in good yield.12... [Pg.189]

Syntheses of Four-Membered Cyclic Compounds 3.1.2.1 Carbocyclic Compounds... [Pg.55]

Four-membered carbocyclic ring systems are commonly formed by cycloaddition of electrophilic alkenes, ketenes and arynes to enamines. Since cycloaddition reactions of enamines are dealt with in Chapter 18 these reactions will only be mentioned briefly here. [Pg.798]


See other pages where Carbocycles four-member is mentioned: [Pg.160]    [Pg.311]    [Pg.160]    [Pg.311]    [Pg.326]    [Pg.128]    [Pg.1472]    [Pg.8]    [Pg.269]    [Pg.6]    [Pg.88]    [Pg.101]    [Pg.232]    [Pg.166]    [Pg.273]    [Pg.54]    [Pg.134]    [Pg.16]    [Pg.59]    [Pg.80]    [Pg.190]    [Pg.474]    [Pg.1075]    [Pg.267]    [Pg.390]    [Pg.2]    [Pg.84]    [Pg.97]    [Pg.609]    [Pg.396]    [Pg.827]    [Pg.304]    [Pg.327]    [Pg.396]    [Pg.245]    [Pg.54]    [Pg.87]    [Pg.1033]    [Pg.310]    [Pg.101]   


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Four-membered

Four-membered Carbocyclic Systems

Four-membered carbocycles

Four-membered carbocycles

Four-membered carbocycles cycloaddition

Fused Four-membered Carbocyclic Systems

Ketones four-membered carbocycles

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