Cyclobutadienes Cyclobutanes

Cyclobutadiene Cyclobutane Cyclobutanone Cyclobutene Cyclobutyl Bromide... 

Within the cubane synthesis the initially produced cyclobutadiene moiety (see p. 329) is only stable as an iron(O) complex (M. Avram, 1964 G.F. Emerson, 1965 M.P. Cava, 1967). When this complex is destroyed by oxidation with cerium(lV) in the presence of a dienophilic quinone derivative, the cycloaddition takes place immediately. Irradiation leads to a further cyclobutane ring closure. The cubane synthesis also exemplifies another general approach to cyclobutane derivatives. This starts with cyclopentanone or cyclohexane-dione derivatives which are brominated and treated with strong base. A Favorskii rearrangement then leads to ring contraction (J.C. Barborak, 1966). 

Conjugated chains, 14, 46 Correlation diagrams, 44, 50 Cyclobutadiene, 171 Cyclobutane, 47, 222 orbital ordering, 26 through-space interactions, 26 Walsh orbitals, 27 Cyclobutene, 200 Cyclohexane, 278 Cyclohexene (half-boat), 274 Cyclopen tadiene, 225 Cvclopen tadienone, 269 Cyclopentadienyl anion, 237 Cyclopentane, 254 Cyclopen ten e, 241 Cyclopropane, 41, 47, 153 construction of orbitals, 19, 22 Walsh orbitals, 22, 36, 37 Cyclopropanone, 48, 197 bond lengths, 38 Cyclopropen e, 49, 132 reactivity, 40... 

That bond-bending strain is not confined to three-membered rings is evident from charge density studies on cyclobutane (Stein et al. 1992), cyclobutadiene... 

Azete, azetine and azetidine are the aza analogues of cyclobutadiene, cyclobutene and cyclobutane, respectively (Box 8.1). 

A silver-cyclobutadiene complex is obtained when the mercury-containing, bromine-free oil, obtained by treatment of 1,2,3,4-tetrabromo-cyclobutane with lithium amalgam, is treated with silver nitrate (5). The complex forms colorless crystals which, on treatment with steam, evolve... 

Nonacarbonyldiiron in the presence of activated zinc as well as disodium tetracarbonylferrate have both been utilized to dechlorinate dimethyl cispransjransA,2,3,4-tetrachlorocyclobutane-1,2-dicarboxylate (41), which leads to [dimethyl l,2,3,4- 7-l,3-cyclobutadiene-l,2-dicarboxy-latejiron tricarbonyl (42) in 1 and 35-40% yield, respectively.15 As a result of the better leaving tendency of the bromide anion, the yield of 42 can be improved to 70% by reaction of the analogous dibromide with nonacarbonyldiiron in dimethylformamide.16 In another experiment, debromination with activated zinc in tetrahydrofuran converts cyclobutane-1,2-di-carboxylate 43 to cyclobutene-1,2-dicarboxylate 44 in 58% yield.15... 

Cycloaddition reactions, 162-165, 197-198 component analysis, 168 Diels-Alder, 162, 198 ethylene + ethylene, 198 orbital correlation diagram, 198 stereochemistry, 162-163 Cycloalkanols, synthesis, 277 Cyclobutadiene barrier, 91 ground state, 91 point group of, 5 self-reactivity, 97 SHMO, 151 structure, 309-310 Cyclobutane... 

Cyclobutadien Trimethyl- E17f., 1066 [ AIBr3 (-+ En)] Cyclobutan Cyclopropyliden El9b, 288 (Carben + En)... 

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