A modular method to synthesize acridine derivatives was developed with o-acylanilines and diaryliodonium salts. The reactions proceeded smoothly under Cu-catalyzed or metal-free reaction conditions at elevated temperature through tandem arylation/Friedel–Crafts reactions.

An efficient and straightforward five-component cascade protocol has been developed to synthesize the highly substituted dispiroindenoquinoxaline pyrrolidine derivatives from ninhydrin, 1,2-phenylenediamine, sarcosine, 1,3-indanedione, and aldehydes via cascade reactions under mild conditions, in which 1,3-dipole azomethine ylide and the dipolarophile were simultaneously generated in situ. This novel method is complementary to the classical Huisgen cycloaddition in that it is well-suited to the preparation of dispiroindenoquinoxaline pyrrolidine derivatives.

An efficient I₂-catalyzed synthesis of thiazolylidenes and 1,4-dithiines from β-ketothioamides (KTAs) has been developed by only controlling the amount of I₂ that triggers different cascade reaction sequences by means of [3+2] or [3+3] cyclocondensation in a one-step process. A possible mechanistic proposal for these transformations is presented.

Imidazo[1,2-a]pyridines have been successfully synthesized in moderate to good yields via a tandem three-component reaction of ethyl 2-(3-oxo-3-arylpropanethioamido)acetates with aromatic aldehydes and malononitrile by means of microwave irradiation using DABCO as the catalyst. The advantages of this method including high chemo- and regioselectivity make this new strategy highly attractive.

Two series of previously unknown spiro-pyrrolidine derivatives were prepared by a five-component reaction that employed ninhydrin, 1,2-phenylenediamine, sarcosine, aldehydes, and malononitrile or cyanoacetic ester in a solvothermal synthesis. This is the first report of an autocatalytic five-component reaction involving a classical Huisgen reaction, in which the dipole – an azomethine ylide – and the dipolarophile were simultaneously generated in situ. The 1,3-dipolar cycloaddition reaction was found to proceed in a highly regio- and diastereoselective manner. The methodology for the preparation of the spiro-pyrrolidines could be an ideal tool for green chemistry and the synthesis of alkaloids.

Two series of dispiropyrrolidine derivatives were successfully synthesized by a tandem Knoevenagel–1,3-dipolar cycloaddition reaction sequence of isatin or acenaphthylene-1,2-dione, sarcosine, 1,3-indanedione, and an aldehyde without any catalyst. This strategy is not only suitable to aromatic aldehydes but aliphatic and heteroaromatic aldehydes as well. Moreover, this one-pot, four-component synthesis of dispiropyrrolidines is the first of its kind, as the dipole azomethine ylide and dipolarophile can be generated in situ. Such a strategy would provide access to a fast one-pot synthesis of dispiroheterocycles, which are otherwise accessible only through multistep synthesis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)