Alkynes aromatic homologation

The combination of [IrCl(cod)Cl]2 complex with P(t-Bu)3 efficiently catalyzes aromatic homologation using internal alkyne [70]. For example, the reaction of benzoyl chloride 153 with 4-octyne 154 afforded 1,2,3,4-tetrapropylnaphthalene 155 (Equation 10.41). The reaction with 2-thenoyl and 2-naphthoyl chlorides also affords benzothiophene and anthracene, respectively, in high yields. The reaction would proceed as follows (Scheme 10.9) (i) oxidative addition of aroyl chloride... 

Rhodium(II) acetate catalyzes C—H insertion, olefin addition, heteroatom-H insertion, and ylide formation of a-diazocarbonyls via a rhodium carbenoid species (144—147). Intramolecular cyclopentane formation via C—H insertion occurs with retention of stereochemistry (143). Chiral rhodium (TT) carboxamides catalyze enantioselective cyclopropanation and intramolecular C—N insertions of CC-diazoketones (148). Other reactions catalyzed by rhodium complexes include double-bond migration (140), hydrogenation of aromatic aldehydes and ketones to hydrocarbons (150), homologation of esters (151), carbonylation of formaldehyde (152) and amines (140), reductive carbonylation of dimethyl ether or methyl acetate to 1,1-diacetoxy ethane (153), decarbonylation of aldehydes (140), water gas shift reaction (69,154), C—C skeletal rearrangements (132,140), oxidation of olefins to ketones (155) and aldehydes (156), and oxidation of substituted anthracenes to anthraquinones (157). Rhodium-catalyzed hydrosilation of olefins, alkynes, carbonyls, alcohols, and imines is facile and may also be accomplished enantioselectively (140). Rhodium complexes are moderately active alkene and alkyne polymerization catalysts (140). In some cases polymer-supported versions of homogeneous rhodium catalysts have improved activity, compared to their homogenous counterparts. This is the case for the conversion of alkenes direcdy to alcohols under oxo conditions by rhodium—amine polymer catalysts... 

Subsequent protic workup releases the aromatic compound. The metalative Reppe reaction can also be used to prepare iodo-substituted or homologated aromatics by treatment of the titanium aryl compound with iodine or an aldehyde, respectively. This procedure has recently been extended to include pyridine derivatives (254 and 255), where the titanacyclopentadiene intermediate can be treated with sulfonylnitriles to afford pyridines after protic workup.192 As with the alkyne cyclotrimerizations, treatment with the appropriate electrophiles affords iodo- and homologated pyridines. 

To avoid the direct manipulation with hazardous azides, methods using Cu(I)situ generation of azides were developed as one-pot procedures, for example, with substitution reaction of alkyl hahdes by NaN3 [493] or with nitrosation of aromatic primary amines by tBuONO followed by trimethylsilyl azide [494]. Vice versa, the alkyne component has been generated in situ, for example, by sequential Seyferth-Gilbert reaction (homologation of aldehydes with diazophosphonates) and reaction with azides in a Cu(l)-catalyzed cycloaddition [495]. 

Fused aromatic compounds such as polyacenes have attracted much attention as organic conductive materials. However, established methods are very limited. Lack of general and convenient synthetic methods for fused aromatic compounds and their very poor solubility in organic solvents are the most serious problems that control further advances in this very important field. Taka-hashi and coworkers have recently developed a synthetically useful method for preparation of fused aromatic compounds, by using the zirconocene-mediated aromatization of alkynes. In order to solve the solubility problem, alkyl substituents are introduced into to the skeletons. In principle, two types of synthetic protocols have been used. Type I protocol is via the homologation starting from a functionalized benzene derivative (Scheme 3) [75] the Type II protocol is via the intermolecular cycloaddition of two alkynes to an arene (Scheme 4) [76]. 

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