- Imamura H Shimizu A Sato H Sugimoto Y Sakuraba S Nakajima S Abe S Miura K Nishimura I Andamad 1 (139.95 KiB) Viewed 117 times
Imamura, H.; Shimizu, A.; Sato, H.; Sugimoto, Y., Sakuraba, S.; Nakajima, S.; Abe, S.; Miura, K.; Nishimura, I.; andamada, K.; and Morishima, H., Tetrahedron, 56, 7705 (2000). Me SOCI2. Py Exercise 2 Ме н INCO.Me 6 CH, OH BocHN BocHN CO2Me Answer 2 1- Thionyl chloride transforms the alcohol into an alkyl chloride. 2- The amide oxygen displaces intramolecularly the chlorine atom. Evans, D.A.; Gage, J.R.; and Leighton, J.L., J.Am. Chem. Soc., 114, 9434 (1992). Aco BB! Br Aco Exercise 3 OAC ОАс OAC OAC Answer 3 1- The Lewis acid BBr3 complexes with the ether oxygen, which becomes a good- leaving group. 2– The complex delivers a bromide anion that attacks the alkene via an SN2 mechanism. This leads to a double-bond migration and expulsion of the ether oxygen. Jotterand, N.; and Vogel, P., J.Org. Chem., 64, 8973 (1999). OH HO -OH HO H Exercise 4 OH HO Me Mé Answer 4 1- The hemiacetal hydroxy group is protonated, thus becoming a good-leaving group. An elimination gives rise to one of the double bonds of the final furan. 2- The oxygen of the remaining tetrahydrofuran suffers elimination, after protonation, producing the second double- bond in the final furan ring. Yu, P.; Andang, Y.; Zhang, Z.Y.; Mak, T.C.W., and Wong, H.N.C., J.Org. Chem., 62, 6359 (1997). NH TSCI (2.1 equiv.). aqueous NaOH-MeOt-Bu TsN, Exercise 5 НО. Answer 5 1-Both the alcohol and the amine are tosylated. 2- Under the biphasic basic conditions, an anion formed on the nitrogen of the sulfonamide displaces the tosylate. Sledeski, A.W.; Kubiak, G.G., O'Brien, M.K.; Powers, M.R.; Powner, T.H.; and Truesdale, L.K., J.Org. Chem., 65, 8114 (2000). Bno OTS BOH OH K CO, EtOH, ref Exercise 6 Bn0 Bn0 NH2 Bn0- Bn0 Answer 6 1- The amine attacks intramolecularly the epoxide, producing its opening and the formation of an alcohol. 2- The amine displaces the tosylate.