Synthesis of Unsymmetric Sulfonamides

Shahnaz Ghassemi and Kristin Fuchs from Biotage, Virginia have reported on a general method for the synthesis of a set of unsymmetric sulfamides in combination with an alternative method for a Boc-removal strategy (Mol. Diversity 2005, 9, 295. DOI: 10.1007/s11030-005-7456-z). The first step was a one-pot synthesis of Boc-protected sulfamides, followed by N-alkylation via Mitsunobu reaction to introduce more diversity. Silica-bonded phenylsulfonic acid (Si-TsOH) was used for Boc-removal, which was possible in 5 minutes at 100 °C for all examples. All synthesis steps have been performed using microwave heating. For releasing the sulfamides from Si-TsOH, NH₃ in MeOH was used.

Pd-Catalyzed Amination of Aryl Nonaflates

Stephen L. Buchwald and his group from the Massachusetts Institute of Technology, Cambridge have described a fast protocol for the coupling of (hetero)aryl nonaflates and amines (J. Org. Chem. 2005, 71, 430. DOI: 10.1021/jo052131u). An excellent functional group tolerance was observed for the synthesis of diverse arylamines using the catalyst systems Pd₂dba₃ with ligands 1, 2 or 3 respectively, and the soluble amine bases DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) and MTBD (7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene).

Suzuki-Couplings with Organotrifluoroborates

In a recent publication Nicholas E. Leadbeater and co-workers from the University of Connecticut have demonstrated the synthesis of functionalized biaryls via Suzuki-coupling (Tetrahedron Lett. 2005, 47, 217. DOI: 10.1016/j.tetlet.2005.10.153). By using potassium organotrifluoroborates as an alternative to boronic acids and ultra low palladium loading (2.5 ppm), efficient coupling with arylhalides could be performed in 5 minutes at 150 °C under microwave irradiation.

Synthesis of 1-Alkyl-4-Imidazolecarboxylates

By applying a “catch and release” strategy, the group of Giampaolo Giacomelli from Università degli Studi di Sassari has synthesized a set of 1-Alkyl-4-imidazolecarboxylates (J. Comb. Chem. 2005, 7, 905. DOI: 10.1021/cc050067o). The resin-bound isocyanoacrylate 1 was prepared under microwave conditions in only 20 minutes, compared to 36 h of oil-bath heating. For the next step, resin 1 was reacted with a set of amines under open vessel microwave conditions to give imidazolecarboxylates 2 in excellent yields and high purities. Furthermore, the solid support could be recycled and used successfully for 3-4 cycles.