An organocatalyzed intramolecular carbonyl-ene reaction was developed to produce carbocyclic and heterocyclic 5- and 6-membered rings from a citronellal-derived trifluoroketone and a variety of aldehydes. A phosphoramide derivative was found to promote the cyclization of the trifluoroketone, whereas a less acidic phosphoric acid proved to be a superior catalyst for the aldehyde substrates.

Novel and efficient Brønsted acid (p-TsOH) catalyzed inter- and intramolecular Friedel-Crafts alkylations have been developed to synthesize selenated three-component coupling and selenation-cyclization indole derivatives. Chemical removal of the phenylseleno moiety was investigated, and the reaction mechanisms were discussed.

A series of pyrimido[4,5-b]quinolines (5-deazaflavines), were synthesized by microwave assisted intramolecular cyclization. The N⁴-substituted-2,4-diamino-6-chloro-pyrimidine-5-carbaldehydes, were prepared by selective monoamination of 2-amino-4,6-dichloropyrimidine-5-carbaldehyde with aliphatic and aromatic amines.

The reaction of ethyl 2-ethynylphenylcarbamate derivative with alkenes in the presence of a palladium(II) catalyst, copper dichloride and tetrabutylammonium fluoride (TBAF) produced 2-substituted 3-ethenylindoles during refluxing. The intramolecular cyclization reaction of ethyl 2-ethynylphenylcarbamates, which have an ethenyl part in the ethynyl group, was also used to produce carbazole deriva...

[reaction: see text] The one-pot synthesis of new 9-alkyl-6-chloropyrido[3,2-e][1,2,4]triazolo[4,3-a]pyrazines has been achieved. Hydrazides regioselectively reacted as nucleophiles with the 3-chloro substituent of 2,3-dichloropyrido[2,3-b]pyrazine. An intramolecular cyclization afforded the tricycle nonxanthine adenosine receptor antagonists.

An efficient palladium/copper-catalyzed approach to the synthesis of highly substituted 3-formyl furans from the reactions of readily available α-bromoenaminones with terminal alkynes has been developed. This methodology was realized by the cascade reactions of Sonogashira coupling and the subsequent intramolecular cyclization.

[reaction: see text] A short synthesis of (+/-)-brazilin is reported. This synthesis uses several interesting and underutilized transformations including a regioselective dirhodium-catalyzed aryl C-H insertion, a regioselective IBX phenol --> o-quinone oxidation, a tautomerization of an o-quinone to a p-quinone methide, and an intramolecular aryl cyclization with a p-quinone methide.

Pyrrolo[2,1-f][1,2,4]triazin-4(3H)-ones 12 have been easily prepared via nucleophile-induced rearrangement of pyrrolooxadiazines 11 and regioselective intramolecular cyclization of 1,2-biscarbamoyl-substituted 1H-pyrroles 10. In this work, we demonstrated that the described synthetic approaches can be considered to be more facile and practical than previously reported procedures.

An efficient synthesis of pyrazoles from tosylhydrazones and nitroalkenes was developed. In comparison with the previously reported 1,3-dipolar cycloaddition reaction of diazo compounds with electron-deficient alkenes or alkynes, this methodology proceeded with a sequential Baylis-Hillman/intramolecular cyclization mechanism and a variety of reversed regioselectivity products were prepared in g...

A review of synthetic methodologies reported in the last five years that yield N-heterocyclic products by intramolecular cyclization of organic azides with a particular emphasis on transformations catalyzed by metal complexes is presented. These reactions have been classified according to the ring size of the formed heterocycle.