Iron-Catalyzed Ring-Opening Azidation and Allylation of O-Heterocycles

Abstract

We have established the first catalytic C-C and C-N bond formation reactions of O-heterocycles (e.g., tetrahydrofuran, phthalane, and lactone derivatives) using iron trichloride as a catalyst in the presence of TMSN3 or allylsilanes accompanied by the ring opening of O-heterocycles. The reactions smoothly proceeded at room temperature to give the corresponding primary saturated alcohols from the 2-substituted tetrahydrofurans, ortho-substituted benzyl alcohols from phthalanes, and saturated carboxylic acids from lactones in high yields.

Iron Catalysis in Organic Synthesis

“…761 These reactions were catalyzed by iron(III) chloride and proceeded under mild conditions in dichloromethane at room temperature giving azidated linear alcohols, benzyl alcohols, or carboxylic acids in high yields. Moreover, allyltrimethylsilanes could be employed as nucleophiles as well providing ring-opened CÀC coupling products (eq b).…”

Azidotrimethylsilane

“…136 Iron(III) chloride also catalyzes the ring-opening azidation of tetrahydrofurans with azidotrimethylsilane to afford the corresponding 4-azidobutan-1-ol in good to excellent yields (eq 50). 137 No reaction occurs when azidotrimethylsilane is replaced by sodium azide or diphenylphosphoryl azide (DPPA). …”

Gold-Catalyzed Benzylic Azidation of Phthalans and Isochromans and Subsequent FeCl₃-Catalyzed Nucleophilic Substitutions

“…[9][10][11][12][13] We have continuously investigated the iron [14][15][16][17][18][19][20] -or gold [21][22][23] -catalyzed activation at the benzylic position of various skeletons accompanied by the benzylic C-O bond cleavage. During these investigations, the benzylic position of phthalan (1; n=1) as a benzene fused cyclic ether was found to be directly azidated in the presence of a gold catalyst and trimethylsilylazide (TMSN 3 ) without the C-O bond cleavage to give the 1-azido phthalan (2) (Chart 1).…”