Aryl derivatives intramolecular cyclization

Diaryltellurides and diarylditellurides undergo a smooth tellurium-zinc exchange reaction in the presence of catalytic amounts of Ni(acac)2 leading to aryl-zinc derivatives. Intramolecular cyclization may also occur 113]. 

A novel hypervalent iodine-induced direct intramolecular cyclization of a-(aryl)alkyl-jS-dicarbonyl compounds 33 has been recently reported (Scheme 15) [30]. Both meta- and para-substituted phenol ether derivatives containing acyclic or cyclic 1,3-dicarbonyl moieties at the side chain undergo this reaction in a facile manner affording spirobenzannulated compounds 34 that are of biological importance. 

Vinyl-l//-isochromenes can be prepared in moderate yield by a palladium-catalyzed coupling of ( )-(3-(2-bromo-phenyl)allyloxy)tenM)i i r l)si Iyl derivatives 157 with ketones. The reaction proceeds via initial ketone arylation to furnish the intermediate 158 followed by intramolecular cyclization of the ketone enolate onto the tethered allylic system (Scheme 50) <2000CG1675>. 

Benzyne generated from 2-iodophenyl 4-chlorobenzenesulfonate by treatment with tropropyl magnesium chloride at low temperature adds to the magnesium thiolate derived from thiosalicylic acid 530 to form thioxanthone. The carboxyl function behaves as an electrophile towards the intermediate aryl magnesium species and an intramolecular cyclization ensues (Scheme 212) <2005AGE4258>. 

The palladium-catalyzed arylation and alkenylation of olefins, which were first discovered in the 1970 s by Heck (7,2) and Mizoroki (3) and have been often called the "Heck reaction", are versatile synthetic means for making a carbon-carbon bond. These reactions have been extensively used for organic synthesis during the past two decades (4-7). However, no reports on the "asymmetric Heck reaction" have been appeared until very recently. Shibasaki reported an asymmetric intramolecular cyclization of alkenyl iodides to give c/j-decalin derivatives of 80-91% ee (8-10). Overman reported an intramolecular cyclization of alkenyl triflate, giving a chiral quaternary carbon center of 45% ee (77). We report herein the first example of intermolecular asymmetric Heck-type arylation of cyclic olefins catalyzed by (7 )-BINAP-coordinated palladium complexes (Scheme 1) (12,13). 

Baylis-Hillman adducts such as 55 and 56 derived from 2-nitrobenzaldehydes were shown to function as useful precursors to functionalized (1H)-quinol-2-ones and quinolines. Treatment of 55 and 56 with iron and acetic acid at 110 °C afforded 57 and 58, respectively <02T3693>. A variety of other cyclization reactions utilized in the preparation of the quinoline scaffold were also reported. An iridium-catalyzed oxidative cyclization of 3-(2-aminophenyl)propanols afforded 1,2,3,4-tetrahydroquinolines <02OL2691>. The intramolecular cyclization of aryl radicals to prepare pyrrolo[3,2-c]quinolines was studied <02T1453>. Additionally, photocyclization reactions of /rans-o-aminocinnamoyl derivatives were reported to provide 2-quinolones and quinolines <02JHC61>. Enolizable quinone and mono- and diimide intermediates were shown to provide quinolines via a thermal 6jt-electrocyclization <02OL4265>. Quinoline derivatives were also prepared from nitrogen-tethered 2-methoxyphenols. The corresponding 2-methoxyphenols were subjected to a iodine(III)-mediated acetoxylation which was followed by an intramolecular Michael addition to afford the quinoline OAc O... 

Intramolecular palladium-catalyzed cyclization reactions have also been used to synthesize pyrazole derivatives. iV-Aryl-iV-(o-bromobenzyl)hydrazines 494 participated in a palladium-catalyzed intramolecular amination reaction to give 2-aryl-2//-indazoles 495 (Equation 101) <20000L519>. Palladium-catalyzed intramolecular C-N bond formation of iV-acetamino-2-(2-bromo)arylindolines 496, followed by hydrolysis and air oxidation in the presence of aluminium oxide, allowed the preparation of indolo[l,2-3]indazoles 498 via intermediate 497 (Scheme 58) <2002TL3577>. 3-Substituted pyrazoles have been prepared from the intramolecular cyclization of A -tosyl-iV-(l-aryl/ vinyl-1-propyn-3-yl)hydrazine and then exposme of the reaction mixture of the cyclization to potassium /i //-butoxide <1997SL959>. iV-Aryl-iV -(o-bromobenzyl)hydrazines 499 or [A -aryl-A -(t>-bromobenzyl)hydrazinato-A ]-triphenyl-phosphonium bromides 501 participated in a palladium-catalyzed intramolecular amination reaction to give 1-phenyl-l//-indazoles 500 (Scheme 59) <2001TL2937>. 

Imines 1110 derived from trifluoromethyl aryl ketones and orT o-phenylenediamines 1109 undergo intramolecular cyclization to afford 2-arylbenzimidazoles 1111. The reaction is carried out under basic conditions and the CF3 group serves as a leaving group (Scheme 268) <1999TL4119>. 

The coelectrolysis of veratrole with anisole derivatives afforded in TFA-CH2CI2 good yields of aryl-substituted triphenylene derivatives (Table 4, number 9). Product formation probably occurs by initial coupling of the veratrole cation radical with anisole to an unsymmetrical dimer. This is followed by coupling of the dimer and intramolecular cyclization to the product. 

Cyclopropanols undergo facile reaction with photoexcited aryl ketones such as benzophenone and fluorenone. Irradiation of fluorenone (14) and 1-phenylcyclopropanol gives a 78% yield of the coupling product 15. Spiro product 16, obtained from 1,2,2-trimethylcyclopropanol, may be derived from the y-hydroxy ketone by a further intramolecular cyclization reaction of this initial coupling adduct. 

The ortho-benzylthio derivatives 110 were treated with sulfuryl chloride in di-chloroethane and intermediate compounds sulfenyl chlorides 111 were apparently formed, which underwent intramolecular cyclization due to the interaction of S-Cl fragment with the C = N bond. This pathway results in the formation of 2-aryl-4,6-dinitro-l,2-benzisothiazolium chlorides 112a-d even at room temperature. The structure of salts 112 was established by an NOE method (04MC207, Scheme 36). 

The catalyst was also shown to be effective for the production of indolic and fur-anic derivatives by sp2-sp coupling of aryl halides and alkynes followed by intramolecular cyclization. Again, mild reaction conditions (i.e., 25 °C) were employed and no Cu1 promoter was needed. 

This heterocyclic skeleton is accessible by four methods The first involves an intramolecular cyclization of the enolform of 8-bromo- or 8-chloro-7-(acylalkyl)-purinedione derivatives 39, which were prepared from the potassium salt of 8-bromopurinediones and a-bromodialkyl- or a-bromoalkyl aryl ketones 41 under reflux in dimethylformamide giving derivatives of oxazolo[2,3-/]-purine-2,4-dione 40 (86KGS1133) (Scheme 10). 

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