Benzene intramolecular coupling

Figure 1. Linewidlhs of different rotational transitions in the 14q1q vibronic band of benzene measured with Doppler-free two-photon absorption. The observed strong dependence on the quantum number J of the rotational angular momentum is evidence for a rotationally dependent intramolecular coupling process. (Taken from Ref. 3.)...

H. J. Neusser For a selected intermediate J K> state we observe a couple of Rydberg series for example, for J K, = li we can identify two series under minimum residual field conditions. When we apply a stationary electric field of 300 mV/cm, additional series appear that are coupled by the electric field. All series have different limits representing different rotational states of the benzene cation. At present we cannot say whether the coupling observed under minimum residual field conditions is induced by the small stray field or by field-free intramolecular coupling. 

Oxidative homocoupling of aromatic and heteroaromatic rings proceeds with Pd(OAc)2 in AcOH. Biphenyl (165) is prepared by the oxidative coupling of benzene [104,105], The reaction is accelerated by the addition of perchloric acid. Biphenyl-tetracarboxylic acid (169), used for polyimide synthesis, is produced from dimethyl phthalate (168) commercially [106], Intramolecular coupling of the indole rings 170 is useful for the synthesis of staurosporine aglycone 171 [107]. 

When the methyl substituted derivatives of u-bis(phenylsulfonyl)benzene (99) are reduced in DMSO, good yields of the intramolecularly coupled products are obtained. These are methyl-substituted dibenzothiophene dioxides (100a), formed after initial cleavage of PhSOo from the radical anion followed by intramolecular attack of the aryl radical on the phenyl group [290] (Scheme 26). 

Photolysis of 4-cyclopropyl-1-phenylbutan-l-one in benzene gave l-phenylcyclohept-4-en-l-ol, via an interesting 1,5-hydrogen migration, together with other products. Photolysis of spiro[2.5]octan-5-one (10) in benzene yielded 4-methylenecycloheptanone (12) via a-cleavage, -scission of the transient cyclopropylmethyl diradical 11, and subsequent intramolecular coupling. ... 

The colourless conjugated macrocycle 666, which consists of twelve benzene rings and twelve acetylene units, has been obtained by palladium-catalysed intramolecular coupling of the iodo compound 665. ... 

The Pd-catalyzed intramolecular coupling of aryl halides or triflates with aromatic rings to give biaryl compounds offers useful synthetic methods. Intramolecular aryla-tion of benzene derivatives was reported first by Ames. Cyclization of 102, catalyzed by Pd(OAc)2 in the presence of DBU, is an example [23]. Pyrimido[4,5-fe]indole was prepared by intramolecular arylation of 4-anilino-5-iodopyrimidine 103 in 86 % yield in the presence of Pd(OAc>2, PPh3 and AcONa in DMF [24]. Cyclization of the monobrominated diarylpyrazole 104 afforded pyrazolo[l,5-/]phenanthridine in 65 % yield in the presence of phosphine-free Pd(OAc>2, Bu NBr, LiCl and K2CO3 in DMF at 110°C [25]. 

An example of the construction of dibenzofurans by palladium-catalyzed C—H arylation was reported by Itatani in 1974 (Scheme 3.4) [17]. Compared with previous methods [18], this reaction could obviate the tedious synthetic route and is suitable for the preparation of substituted dibenzofurans with high efficiency. It should be noted that substituents on the benzene nucleus are believed to reduce the interaction between molecules and favor intramolecular coupling rather than intermolecular dimerization. 

The benzene derivative 409 is synthesized by the Pd-catalyzed reaction of the haloenyne 407 with alkynes. The intramolecular insertion of the internal alkyne, followed by the intermolecular coupling of the terminal alkyne using Pd(OAc)2, Ph3P, and Cul, affords the dienyne system 408, which cyclizes to the aromatic ring 409[281]. A similar cyclization of 410 with the terminal alkyne 411 to form benzene derivatives 412 and 413 without using Cul is explained by the successive intermolecular and intramolecuar insertions of the two triple bonds and the double bond[282]. The angularly bisannulated benzene derivative 415 is formed in one step by a totally intramolecular version of polycycli-zation of bromoenediyne 414[283,284],... 

Benzenediazonium fluoroborate, 2-carboxy-xanthone synthesis from, 3, 838 Benzenediazonium ions phenyl azide formation from, 5, 839 Benzenediazonium salts, o-(imidazol-l-yl)-intramolecular diazo coupling, 5, 404 Benzene-1,2-disulfonimides N-substituted reactions, 6, 930 Benzene episulfide formation, 7, 577 Benzeneimine... 

Corriu et al. have reported that the coupling reaction of 2-(iV,iV-dimethylaminomethyl)phenyllithium with (McvSi)vSiCI 53 affords 2-(iV,iV-dimethylaminomethyl)-l-[tris(trimethylsilyl)silyl]benzene 894. No evidence has been found that the intramolecular iV-ligand coordinates to the silicon atom of 894. Upon UV irradiation, the trisilane forms a transient silyene 895, which has been trapped with 2,3-dimethyl-2,3-butadiene and triethylsilane to give the oligosilanes 896 and 897 as well as 898-900, (Scheme 126).859 Apparently, the bulk on the two ligands is insufficient to provide kinetic stabilization of the silylene intermediate 895. 

Intramolecular cross-coupling can also be carried out as illustrated in the ring closure of Eq. 6 catalyzed by a nickel complex (L = l,2-bis-(diisopropyl phosphino)benzene) [25] ... 

Benzene hydrocarbons are known to undergo radical coupling reactions and the intramolecular reductive coupling of carbonyl compounds with a benzene ring has been achieved. Best conditions for this process are at a tin cathode with isopropanol solvent and tetaethylammonium tosylate as supporting electrolyte [102, 103], The reaction is performed at constant current in a divided cell. A single stereoiso-... 

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