Indole 5-fluoro-3- -, ring

Regioselective fluorodestannylation of alkenyl and heteroaryl molecules to give 34 can be achieved under mild conditions with cesium fluoroxysulfate, while x-fluoro ketones, e.g. 35, are formed when the tin group is attached to the benzylic position.42 The pyrrole ring in indole derivatives is also successfully fluorinated using this method, e.g. formation of 36.42-45... 

The fluorination of 1-substituted indole 32 with F-Teda BF4 (6) in acetonitrile or acetonitrile/ methanol gives 3-fluoro-2-methoxy-l-tosyl-2,3-dihydroindole (33) in 48% isolated yield.87 Relative stereochemistry about the 2,3-bond in the dihydropyrrole ring was confirmed as trans by X-ray crystallographic analysis. F-Teda BF4 (6) reacts with 2- and 3-trimethylstannyl-sub-stituted 1-tosylindoles to give the corresponding fluoroindoles in 40 and 21 % yield, respectively.108... 

The 8-fluoro-Y-carboline 166 is prepared by a standard Fisher indole synthesis. The condensation of 4-fluorophenylhydrazine (164) with 165. 4-Phenyl compound 168 is synthesized by acid-catalyzed ring closure of 167 (Scheme 12.24). ... 

Li and Tu have described an innovative three-component domino reaction for the synthesis of multifunctionalized tetracyclic indeno[l,2-h]indole derivatives (Scheme 6.30) [59]. Ninhydrin 205 was used to test the allyUc esterification, but the desired product 208 was not observed during this process. Indeed, a novel polysubstituted tetracyclic indeno[l,2-fc]indole derivative 207 was obtained. Li and Tu tested then the best conditions and found out that the reaction proceeds nicely in acetic anhydride under microwave conditions in 20-32min with 63-87% yield (Scheme 6.30a). Electron-withdrawing substituents like fluoro, chloro, and bromo in the para-position of the benzene ring as well as electron-donating substituents (Me, OMe) are well tolerated in this reaction. Bulky residues do not cause any problems. 

Scope and Limitations. Carbonyl Component. For practice purposes this reaction is limited to aromatic aldehydes, of which a wide variety has been studied, and to a,/3-unsaturated aliphatic aldehydes. The sub-stitutents on the ring of the aromatic aldehydes include alkyl, fluoro, chloro, bromo, iodo, hydroxyl, alkoxy, acyloxy, carbethoxy, nitro, and various combinations of two or more of these groups. Aldehydes of the naphthalene, pyrene, biphenyl, thiophene, furmi, pyrrole, indole, chro-mane, coumarane, and thiazole series also have been employed. 

Although requiring high temperatures and long reaction times for the fluorination of aromatic compounds, A-fluoro-2,4,6-tri-methyl triflate (2) was also used for the fluorination of estrone, methyl /J-hydroxyphenylacetate, and some heteroaromatic rings such as indoles or antipyrine derivatives. However, furan, pyrrole, A -benzylpyrrole, ethyl 2-thienylacetate, or methyl 2-thio-phenecarboxylate could not be lluorinated with reagent 2. ... 

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