Multi-step reaction with 7 steps 1: 99 percent / diethyl ether / 20 h / Ambient temperature2: 1-ethyl-3-<3-(dimethylamino)propyl>carbodiimide / CH2Cl2 / 20 h / Ambient temperature; or in THF3: toluene / 18 h / 100 °C4: 73 percent / toluene / 24 h / Ambient temperature5: 83 percent / dioxane / 5 h / Irradiation6: 39 percent / dioxane / Irradiation; repeated portionwise addition of dipolarophile7: 75 percent / Ti(OiPr)4 / 40 h / Heating