In the past decade N-tosylhydrazones emerged as partners in metal-catalyzed and also in metal-free coupling reactions for the formation of carbon-carbon and carbon-heteroatom bonds. One reason for this is that aliphatic and aromatic tosylhydrazones are readily available and stable compounds, and diazo compounds and carbenes, key-intermediates in coupling reactions, can be generated from N-tosylhydrazones in situ [1, 2]. On the contrary, anhydro-aldose tosylhydrazones 1 are not readily available, and their preparation needs special methods. We have elaborated a synthetic method to get such types of compounds by reduction of glycosyl cyanides followed by in situ trapping of the intermediate imine by tosylhydrazine [3, 4]. Based on these preliminaries we have started to examine systematically the coupling reactions of anhydro-aldose tosylhydrazones. It is known from the literature that coupling of N-tosylhydrazones with boronic acids results in C-C bond formation [5, 6]. Our goal was to study some new metal free and metal-catalyzed coupling reactions of ester and ether protected anhydro-aldose tosylhydrazones 1. The metal-free couplings gave the ring-opened heptenitols 2 while metal-catalyzed reactions resulted in substituted exo-glycals 3 (See Figure 1).
The research was supported by the EU and co-financed by the European Regional Development Fund under the project GINOP-2.3.2-15-2016-00008, and by the National Research, Development and Innovation Office under the project FK128766.
- Qiu, D; Mo, F. Y.; Zhang, Y.; Wang, J. B. Recent advances in transition-metal-catalyzed cross-coupling reactions with N-tosylhydrazones. In Advances in Organometallic Chemistry; Perez, P. J., Ed.; Academic Press, 2017; Vol. 67; p 151-219.
- Xia, Y.; Qiu, D.; Wang, J. B. Chem. Rev. 2017, 117, 13810-13889.
- Tóth, M.; Somsák, L. Tetrahedron Lett. 2001, 42, 2723-2725.
- Tóth, M.; Kövér, K. E.; Bényei, A.; Somsák, L. Org. Biomol. Chem. 2003, 1, 4039-4046.
- Barluenga, J.; Tomás-Gamasa, M.; Aznar, F.; Valdés, C. Nat. Chem. 2009, 1, 494-499.
- Zhao, X.; Jing, J., Lu, K.; Zhang, Y.; Wang, J. Chem. Commun. 2010, 46, 1724-1726.