No abstract

An efficient direct approach to triazole-fused sultams has been developed. The key step of the proposed strategy is base-mediated cyclization of sulfonamide-tethered 5-iodo-1,2,3-triazoles which are readily available via an improved protocol for Cu-catalyzed 1,3-dipolar cycloaddition. The annulation of the sultam fragment to the triazole ring proceeds smoothly under transition-metal-free conditions in the presence of Cs2CO3 in dioxane at 100 °C and affords fused heterocycles in high yields up to 99%. The favorability of an SNAr-like mechanism for the cyclization was supported by DFT calculations. The applicability of the developed procedure to modification of natural compounds was demonstrated by preparation of a deoxycholic acid derivative.

Cu-catalyzed Pd-free Sonogashira coupling has been proposed as a straightforward and convenient route to valuable steroidal enynes. A biligand catalyst system based on Ph3P and TMEDA has been designed. The protocol was utilized for the efficient coupling of iodosteroids with diverse terminal alkynes and 1-trimethylsilylalkynes. A possible role of an auxiliary ligand as a phase-transfer catalyst for a sparingly soluble inorganic base (K2CO3) was revealed.

Copper‐catalyzed coupling of π‐deficient NH‐azoles with vinylboronic acids or vinyltrifluoroborate salt provides a direct route to N2‐vinyl‐1,2,3‐triazoles and N2‐vinyltetrazoles. The coupling reaction is efficiently catalyzed by (phen)Cu(PPh3)Br with low catalyst loading (5 mol%) under base‐free conditions. The method is applicable for vinylation of unsubstituted, monosubstituted, and disubstituted 1,2,3‐triazoles with various functionalities with high N2‐selectivity.magnified image