Compounds carbocydic

On the other hand, the reaction of bisallenes with Bu3SnSnBu3 may generate cis-bisallene Pd(SnBu3)2 (C) and/or a chelated cj-allylpalladium complex D reversibly. The fast carbocydization of these intermediates would give rise to a vinylpalladium complex E, which then yields a ds-compound by reductive elimination and/or a cis-bicyclodiene through (T-bond metathesis as a kinetically controlled product (Scheme 16.66). 

The construction of carbocydic compounds by ring-annulation procedures frequently plays a prominent role in total synthesis. The tolerance of various functional groups in the zinc reagents employed in copper-catalyzed asymmetric 1,4-additions forms the basis for three novel catalytic enantioselective annulation methods discussed here. 

Cyclopentadienyl compounds are by far the most important of all carbocydic 71 complexes, and the C5HS ligand or substituted derivatives such as MeQH or Me5C5 are widely used. The QH5 group is commonly abbreviated as Cp, Me5C5 as Cp, and other substituted spedes as Cp or Cp". 

Quite recently, novel cyclization reactions involving CO to give carbocydic and heterocyclic compounds, which are characteristic for mthenium catalysts, have been developed. Ruthenium complexes provide new avenues for cydization reactions. In addition, CO is often used as a reducing agent, and reductive carbonylations of nitro compounds catalyzed by mthenium complexes are very attractive reactions that provide phosgene-free processes [3]. 

This catalytic sequence is known as Kharasch addition or atom transfer radical addition (ATRA) [4]. Various polyhalogenated compounds such as CCI4 and CCI3CO2R are used as the organic halides, and transition metal salts or complexes are used as the catalyst [3]. Intramolecular version of the Kharasch addition reaction (atom transfer radical cyclization, ATRC) has opened novel synthetic protocols to the synthesis of carbocyde or heterocyles catalyzed by transition metals [5-7], and this has become a very important field in free radical cydization in organic synthesis. Transition metal-catalyzed Kharasch reactions sometimes afford telomers or poly-... 

Scheme 2 Carbocydic compounds from furanose sugars.

The most important 10ft carbocydic system is naphthalene (19) in which two benzene rings are fused together. The fused systems anthracene (20) and phenanthrene (21) obey Hiickd s rule, where n = 3, and have 14ft-electrons. All three compounds are typically aromatic and their chemistry is similar to that of benzene, as discussed in Chapter 12. 

Carbocydic compound A ring of only carbon atoms. 

Metal TT-Comp/exes Formed by Seven-Membered and Eight-Membered Carbocydic Compounds... 

This family of foidamers consists of two, three, or five alternating aromatic heterocydes (pyridazine, pyrimidine, or pyrazine) and methyl-substituted aromatic carbocycles (tolyl, o-xylyl, or m-xylyl) cormected via urea groups (8 Figure 9.3) [14]. In a typical synthesis, heterocyclic diamine compounds were treated with aryl diisocyanate compounds to install a urea linkage between aromatic heterocyde and aromatic carbocyde (Umax = 5). 

Subsequendy, the aromaticity concept built on carbocydes has been applied successfully to heterocyclic organic compounds, i.e., to a family of aromatic compounds which contain one or more heteroatoms as a part of their cyclic TC-electron system. However, some of the measures developed for aromatic hydrocarbons, particularly those based on geometrical parameters, have been modified to be used for heterocycles (1993JCI70, 2001T5715, 2010SY1485). 

Conjugate reduction of a, 3-unsaturated carbonyl compounds and subsequent carbon-carbon bond formation provides a versatile domino process of carbocyde and heterocyle synthesis [20]. These reactions proceed by the formation of enolate 49 through conjugate reduction of a,P-unsaturated carbonyl compound 48 with a reducing agent (M-H) followed by trapping of the enolate with an electrophile 50 to give 51 (Scheme 9.11). 

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