http://www.mdpi.com/journal/molecules/special_issues/cycloadd-reaction/ Dear Colleagues, Cycloaddition reactions provide rapid access to natural and unnatural compounds of medicinal interest or intermediates useful for functional materials. In general, cycloadditions represent an efficient entry to ring systems and require readily available starting materials. In addition, many cycloaddition reactions tolerate a wide variety of functional groups. The focus of this special issue is to present papers that cover both fundamental and applied contributions in this field. Special attention will be paid to the development of new methodologies, mechanistic analysis of existing methodologies, and applications of cycloaddition reactions toward the synthesis of pharmalogically or industrially relevant materials. Prof. Dr. Janis Louie Guest Editor {snippet name="submission_info"} http://www.mdpi.com/1420-3049/16/3/2304/ Some new heterocyclic compounds containing isoxazole, pyrazole and oxadiazole ring systems were prepared from various chalcones. The synthesized compounds have been characterized by elemental analysis and spectral methods. These compounds were screened for their antimicrobial activities. http://www.mdpi.com/1420-3049/16/3/2304/ Wed, 09 Mar 2011 00:00:00 CET Molecules 2011-03-09 16 3 Article 2304 2312 1420-3049 Synthesis and Antimicrobial Evaluation of Some Heterocyclic Chalcone Derivatives 2011-03-09 doi: 10.3390/molecules16032304 Nagwa Mohamed Mahrous Hamada Essam Mohamed Sharshira http://www.mdpi.com/1420-3049/16/3/1956/ 6-[(4-Methoxy/4,9-dimethoxy)-7-methylfurochromen-5-ylideneamino]-2-thioxo-2,3-dihydropyrimidin-4-ones 1a,b were prepared by reaction of 6-amino-2-thiouracil with visnagen or khellin, respectively. Reaction of 1a,b with methyl iodide afforded furochromenylideneaminomethylsulfanylpyrimidin-4-ones 2a,b. Compounds 2a,b were reacted with secondary aliphatic amines to give the corresponding furochromen-ylideneamino-2-substituted pyrimidin-4-ones 3a–d. Reaction of 3a–d with phosphorus oxychloride yielded 6-chlorofurochromenylidenepyrimidinamines 4a–d, which were reacted with secondary amines to afford furochromenylideneamino-2,6-disubstituted pyrimidin-4-ones 5a–d. In addition, reaction of 5a–d with 3-chloropentane-2,4-dione gave 3-chloro-furochromenylpyrimidopyrimidines 6a–d. The latter were reacted with piperazine and morpholine to give 1-(furochromenyl)-pyrimidopyrimidine-3,6,8-triylpiperazines or -3,6,8-triylmorpholines 7a–d. The chemical structures of the newly synthesized compound ware characterized by IR, 1H-NMR, 13C-NMR and mass spectral analysis. These compounds were also screened for their analgesic and anti-inflammatory activities. Some of them, particularly 3–7, exhibited promising activities. http://www.mdpi.com/1420-3049/16/3/1956/ Fri, 25 Feb 2011 00:00:00 CET Molecules 2011-02-25 16 3 Article 1956 1972 1420-3049 Synthesis of New Visnagen and Khellin Furochromone Pyrimidine Derivatives and Their Anti-Inflammatory and Analgesic Activity 2011-02-25 doi: 10.3390/molecules16031956 Ameen Ali Abu-Hashem Mohamed M. Youssef http://www.mdpi.com/1420-3049/16/1/119/ [2+2] Photocycloaddition of olefins is a very useful reaction in synthetic organic chemistry to obtain cyclobutane-containing molecules, which are almost inaccessible by other methods. The reaction, when performed in the crystalline state, occurs more efficiently and selectively than in homogeneous solution due to tight and regular molecular arrangement in the crystal state. Despite numerous examples for the solid-state [2+2] photodimerization of monoenes, however, it is still a challenge to prepare not only dimers but also higher oligomers and polymers from conjugated polyenes, which have multiple reactive double bonds in a molecule. In our recent studies of the solid-state photoreactions of α,ω-diarylpolyenes, noncovalent intermolecular interactions in crystals were effectively utilized to prealign molecules in stacking arrangements, suitable for the [2+2] reaction. With appropriate ring-substituents, [2+2] photodimerization and photopolymerization of the polyenes took place, although the degree of polymerization was relatively low. This review will describe the details of these reactions. http://www.mdpi.com/1420-3049/16/1/119/ Tue, 28 Dec 2010 00:00:00 CET Molecules 2010-12-28 16 1 Review 119 148 1420-3049 Solid-State [2+2] Photodimerization and Photopolymerization of α,ω-Diarylpolyene Monomers: Effective Utilization of Noncovalent Intermolecular Interactions in Crystals 2010-12-28 doi: 10.3390/molecules16010119 Yoriko Sonoda http://www.mdpi.com/1420-3049/15/12/9437/ This review covers the application of cycloaddition reactions in forming the boron-containing compounds such as symmetric star-shaped boron-enriched dendritic molecules, nano-structured boron materials and aromatic boronic esters. The resulting boron compounds are potentially important reagents for both materials science and medical applications such as in boron neutron capture therapy (BNCT) in cancer treatment and as drug delivery agents and synthetic intermediates for carbon-carbon cross-coupling reactions. In addition, the use of boron cage compounds in a number of cycloaddition reactions to synthesize unique aromatic species will be reviewed briefly. http://www.mdpi.com/1420-3049/15/12/9437/ Tue, 21 Dec 2010 00:00:00 CET Molecules 2010-12-21 15 12 Review 9437 9449 1420-3049 Application of Cycloaddition Reactions to the Syntheses of Novel Boron Compounds 2010-12-21 doi: 10.3390/molecules15129437 Yinghuai Zhu Xiao Siwei John A. Maguire Narayan S. Hosmane http://www.mdpi.com/1420-3049/15/12/9230/ Polyalkyne and enediyne azamacrocycles are prepared from arenesulfonamides and various alkyne and alkene derivatives either under basic or neutral conditions. The new family of macrocyclic substrates is tested in the [2+2+2] cycloaddition reaction. Several catalysts are used for the cycloisomerization reaction, and their enantioinduction is evaluated as appropriate. The effect of the structural features of the macrocycles, namely the ring size, substituents in precise positions and the number and type of unsaturations, on the [2+2+2] cycloaddition reaction has also been studied. http://www.mdpi.com/1420-3049/15/12/9230/ Wed, 15 Dec 2010 00:00:00 CET Molecules 2010-12-15 15 12 Review 9230 9251 1420-3049 [2+2+2] Cycloaddition Reactions of Macrocyclic Systems Catalyzed by Transition Metals. A Review 2010-12-15 doi: 10.3390/molecules15129230 Anna Pla-Quintana Anna Roglans http://www.mdpi.com/1420-3049/15/6/4189/ A novel rhodium-catalyzed linear codimerization of alkyl phenyl ketenes with internal alkynes to dienones and a novel synthesis of furans by an unusual cycloaddition of diaryl ketenes with internal alkynes have been developed. These reactions proceed smoothly with the same rhodium catalyst, RhCl(PPh3)3, and are highly dependent on the structure and reactivity of the starting ketenes. http://www.mdpi.com/1420-3049/15/6/4189/ Wed, 09 Jun 2010 00:00:00 CEST Molecules 2010-06-09 15 6 Article 4189 4200 1420-3049 Rhodium-Catalyzed Linear Codimerization and Cycloaddition of Ketenes with Alkynes 2010-06-09 doi: 10.3390/molecules15064189 Kondo Niimi Yoshida Wada Mitsudo Kimura Toshimitsu