Quinoline derivative, insertion

An interesting case of C-C cleavage by late transition metals has been reported by Suggs and Cox involving the quinoline derivative [Eq. (6.117)]. In this case, the carbonyl group weakens the a-C-C bond, thereby facilitating kinetically the metal insertion process. 

Treatment of N-2,4-dinitrophenylpyridinium chloride (778) with phenyl-hydrazine in acetic acid causes reductive cyclization to yield the pyrido[l,2-ajimidazole (779). 3-Aminocrotononitrile, MeC(NH2)=CHCN, condenses with quinoline 1-oxide and isoquinoline 2-oxide to form the tricyclic compounds (780) and (781), respectively." The imidazo[5,l-a]isoquinoline derivative (783) is obtained by the action of phenyl isothiocyanate on the sodium salt of the Reissert compound (782)." ° Triethyl phosphite reduces the o-nitrophenyldipyr-rolylmethane (784 R=N02) to the nitrene (784 R = N), which forms the pyrrolo[3,2-6]quinoline derivative (785) by an intramolecular insertion reac-tion." 3-Amino-177-isoindole (786) reacts with acetylacetone in the presence of perchloric acid to yield the pyrimidoisoindolium salt (787). ... 

Oxidative annulations reaction of alkynes is one of the important methods to synthesize fused polycyclic heteroarenes [169-173]. Whereas the above examples show easy ruthenium catalysed insertions of alkynes into aromatic sp C-H bonds efforts have been made with related catalysts to perform the double insertion of alkynes into C-H and heteroatom-hydrogen bonds as a route to a variety of heterocycles. Chae S. Yi, has first shown, using ruthenium(ll) catalyst precursors [RuH(CO)(PCy3)2(NCMe)2]BF4 and preferably Ru3(CO)i2/NH4PF6, the alkenylation and double insertions of alkynes into C-H and N-H bonds for the transformation of indolines with terminal alkynes into quinoline derivatives [(Eq. 86)] [174, 175]. 

Radical Reactions.—Thiazolyl, pyridyl, and other heteroaryl radicals formed by aprotic diazotization of the corresponding heterocyclic amines substitute homolytically on thiophen with the formation of 2-heteroaryl-thiophens as the main products in 20—50% yield. The results of competitive experiments indicate that the reactivity of thiophen in this reaction at 70—80 °C is slightly higher than that of benzene. The currently accepted mechanism of the decomposition of benzoyl peroxide in thiophen has been criticized on the basis of new experimental results. No free thienyl radicals are involved in the reaction, as demonstrated by scavenging experiments, and the bithienyls formed are probably derived from dimerization of a benzoyloxythiophen radical a-complex, with subsequent loss of benzoic acid. Nitrene insertion into the thiophen ring has been observed in the thermal decomposition of 2-(2-azidobenzyl)thiophen and similar compounds, leading to thieno[3,2-6]quinoline derivatives. ... 

Some other ring expansions involving the intramolecular amino Claisen rearrangement of vinylarylaziridine [ 123], the Diels-Alder reaction of indoles with acetylene derivative [124-127] and the dibromocarbene insertion into quinoline enol ethers [ 128] have been used to prepare 1-benzazepines. On the other hand, treatment of 3-chloro-3-phenyl-l,2,3,4,5,6-hexahydro-l-benz-azocin-2-ones with piperidine causes a ring contraction to give 2-phenyl-2-(l-piperidinylcarbonyl)-2,3,4,5-tetrahydro-l//-l-bcnzazepines in an excellent yield [23]. 

Intramolecular carbenoid and nitrenoid insertions are also quite effective for the preparation of peri-condensed heterocycles. Thus, photolysis of 1-naphthyl-1,2,3-triazoles 113 leads to bcnzo[d,e quinolines 115, possibly via carbene intermediate 114 (Scheme 55) <1987J(P1)413>. Similarly, on photolysis or thermolysis of 8-azido-l-arylazonaphtha-lenes 116 naphtho[l,8-<7, ]triazine derivatives 117 are formed along with A-aryhminobenzo[/y/]indazoles 118 (Scheme 56) <1978JOC2508, 1982JOC1996>. 

Reaction of the imine 50, derived from o-iodoaniline and benzaldehyde, with diphenylacetylene afforded a mixture of the quinoline 53 and the isoindolo[2.1-ajindole 56. Formation of the quinoline can be understood by insertion of the C=N bond in 51, which is regarded as 6-endo cyclization of the intermediate 51 to generate 52, followed by -H elimination to yield the quinoline 53. On the other hand, the isoindolo[2.1-a]indole 56 is formed by 5-exo cyclization of 51 to produce 54. The final step is the electrophilic palladation of the a-palladium intermediate 54 to the adjacent aromatic ring to give 55, and reductive elimination gives rise to 56 [18]. The isoindolo[2.1-a]indole 59 was obtained in high yield from alkylarylacetylene 58 and the imine 50 [19]. 

As a prehminary interpretation, primary formation of an activated N-acyHsoquino-hnium salt, dediazoniative addition of the a-diazocarbonyl compound to the iminium moiety (rationalized by intermediate 25) with insertion to the isoquinoHne N-C-1 bond, and subsequent HX eHmination (25 26) can be discussed. Quinoline reacts analogously, giving rise to lH-benzo]b]derivatives. 

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