Ylide compounds heteroatoms

Muller et al. have also examined the enantioselectivity and the stereochemical course of copper-catalyzed intramolecular CH insertions of phenyl-iodonium ylides [34]. The decomposition of diazo compounds in the presence of transition metals leads to typical reactions for metal-carbenoid intermediates, such as cyclopropanations, insertions into X - H bonds, and formation of ylides with heteroatoms that have available lone pairs. Since diazo compounds are potentially explosive, toxic, and carcinogenic, the number of industrial applications is limited. Phenyliodonium ylides are potential substitutes for diazo compounds in metal-carbenoid reactions. Their photochemical, thermal, and transition-metal-catalyzed decompositions exhibit some similarities to those of diazo compounds. 

Electron deficient species can attack the unshared electron pairs of heteroatoms, to form ylides, such as in the reaction of thietane with bis(methoxycarbonyl)carbene. The S —C ylide rearranges to 2,2-bis(methoxycarbonyl)thiolane (Section 5.14.3.10.1). A"-Ethoxycar-bonylazepine, however, is attacked by dichlorocarbene at the C=C double bonds, with formation of the trans tris-homo compound (Section 5.16.3.7). 

An ylide can be defined as a compound in which a carb-anion is attached directly to a heteroatom carrying a high degree of positive charge ... 

The ylides may be defined as dipolar compounds in which a carbanion is covalently bonded to a positively charged heteroatom. They are represented by the following general formula ... 

There are a few isolated cases of the addition of amines, thiols, carboxylic acids, and a phosphorus ylide to doubly bonded germanium compounds. Again, the reactions are regioselective, with the nucleophilic portion of the weak acid adding to the germanium and the proton adding to the heteroatom. 

The chemical behavior of heteroatom-substituted vinylcarbene complexes is similar to that of a,(3-unsaturated carbonyl compounds (Figure 2.17) [206]. It is possible to perform Michael additions [217,230], 1,4-addition of cuprates [151], additions of nucleophilic radicals [231], 1,3-dipolar cycloadditions [232,233], inter-[234-241] or intramolecular [220,242] Diels-Alder reactions, as well as Simmons-Smith- [243], sulfur ylide- [244] or diazomethane-mediated [151] cyclopropanati-ons of the vinylcarbene C-C double bond. The treatment of arylcarbene complexes with organolithium reagents ean lead via conjugate addition to substituted 1,4-cyclohexadien-6-ylidene complexes [245]. 

As with any modern review of the chemical Hterature, the subject discussed in this chapter touches upon topics that are the focus of related books and articles. For example, there is a well recognized tome on the 1,3-dipolar cycloaddition reaction that is an excellent introduction to the many varieties of this transformation [1]. More specific reviews involving the use of rhodium(II) in carbonyl ylide cycloadditions [2] and intramolecular 1,3-dipolar cycloaddition reactions have also appeared [3, 4]. The use of rhodium for the creation and reaction of carbenes as electrophilic species [5, 6], their use in intramolecular carbenoid reactions [7], and the formation of ylides via the reaction with heteroatoms have also been described [8]. Reviews of rhodium(II) ligand-based chemoselectivity [9], rhodium(11)-mediated macrocyclizations [10], and asymmetric rho-dium(II)-carbene transformations [11, 12] detail the multiple aspects of control and applications that make this such a powerful chemical transformation. In addition to these reviews, several books have appeared since around 1998 describing the catalytic reactions of diazo compounds [13], cycloaddition reactions in organic synthesis [14], and synthetic applications of the 1,3-dipolar cycloaddition [15]. 

Ylides (pronounced /7-ids) cire important compounds containing a negative carbon atom adjacent to a positive heteroatom. The two important types of ylides cire those that contain phosphorus and those that contain sulfur. 

The following types of dipolarophiles have been used successfully to synthesize five-membered heterocycles containing three heteroatoms by [3 + 2]-cycloaddition of thiocarbonyl ylides azo compounds, nitroso compounds, sulfur dioxide, and Al-sulfiny-lamines. As was reported by Huisgen and co-workers (91), azodicarboxylates were noted to be superior dipolarophiles in reactions with thiocarbonyl ylides. Differently substituted l,3,4-thiadiazolidine-3,4-dicarboxylates of type 132 have been prepared using aromatic and aliphatic thioketone (5)-methylides (172). Bicyclic products (133) were also obtained using A-phenyl l,2,4-triazoline-3,5-dione (173,174). 

The oxygen as heteroatom in ethers or carbonyl compounds is weak to moderate Lewis base. Nevertheless, a highly reactive metal carbene complex can interact with the oxygen to generate oxygen ylide. The interaction between ether and metal carbene functional groups is believed to be rather weak as demonstrated by the facts that other metal carbene reactions, such as G-H insertion and cyclopropanation, can proceed in ethereal solvents." These experiments demonstrate that the formation of the metal ylide is much less favored in the equilibrium shown in Equation (1). ... 

Intramolecular Cycloadditions of Carbonyl Ylides W. Eberbach, J. Brokatzky and H. Fritz, Angew. Chem., Int. Ed. Engl., 1980, 19, 47-48. a,(3-Unsaturated Heteroatomic Compounds in 1,3-Dipolar Addition Reactions V. A. Galishev, V. N. Chistokletov and A. A. Petrov, Russ. Chem. Rev. (Engl. Transl.), 1980, 49, 880-892. 

Ring synthesis from non-heterocycles by closure y to the heteroatom are reported. Sulfonium ylides (135) with active methylene compounds such as malononitrile give a C-phenacyl product (136) however, when reacted with /3-diketones and /3-ketonic esters they produce furans quantitatively (74CL101). In these cases O-phenacylation takes place followed by cyclization to give the 3-hydroxydihydrofuran (137), which is dehydrated to the furan (138) (Scheme 30). These furans differ from those formed by the reaction of the diketone or ketonic esters with phenacyl halides. The latter reaction takes place by C-phenacylation, yielding the isomeric furans (139). 

Current IUPAC and Chemical Abstracts nomenclature has been employed in this index with the former given preference. Substitutive nomenclature has been given preference over radicofunc-tional, additive, subtractive, conjunctive or replacement nomenclature, except where this becomes unwieldy. With many bicyclic and polycyclic compounds bearing heteroatoms, standard bicyclic or polycyclic oxa, aza, and thia replacement nomenclature has often been used. With certain functional groups, where the names are rather complex and probably not familiar to most organic chemists, such as ylides, those compounds have simply been named as sulfur, tellurium and arsonic ylides. Metal catbenes have been treated similarly. With more complex functionality and many heterocycles, the Beilstein Commander Crossfire nomenclature system has been used with certain modifications. 

Carbon functional groups, attachment to polysilanes, 3, 585 Carbon-heteroatom bond formation via antimony(III) compounds, 9, 428 via antimony(V) compounds, 9, 432 via bismuth(III) compounds characteristics, 9, 440 with copper catalysts, 9, 442 non-catalyzed reactions, 9, 443 with bismuth(V) compounds, 9, 450 with bismuthonium salts, 9, 449 with bismuth ylides, 9, 450 Carbon-heteroatom ligands in tetraosmium clusters, 6, 967 in tetraruthenium clusters, 6, 960... 

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