Efficient Oxidative Cleavage of Tetrahydrofuran‐2‐methanols to γ‐Lactones by a 2‐Iodobenzamide Catalyst in Combination with Oxone^®

Abstract

An environmentally friendly oxidative cleavage of tetrahydrofuran-2-methanols to the corresponding g-lactones using ac atalytic amount of 2-iodo-N-isopropylbenzamide hasb een developed. Ther eactiono fv arious tetrahydrofuran-2-methanols with the catalyst in the presence of Oxone (2 KHSO 5 ·KHSO 4 ·K 2 SO 4 )a saco-oxidant in DMF at room temperature successfully affords the corresponding lactones in good to high yields,a nd recovery of the catalyst is readily accomplished using areductive work-up.T his method is notable because it enables the transformation of tetrahydrofuran-2-methanols to g-lactones under mild conditions without the use of any toxicheavy metals.

Hypervalent iodine-mediated synthesis and late-stage functionalization of heterocycles

“…Further, Fujiwara and co-workers reported direct conversion of tetrahydrofuran-2-methanols 97 into γlactones 99 via oxidative cleavage by employing precatalyst, 2-iodobenzamide 98 in the presence of co-oxidant oxone (Scheme 23). 60 Reaction proceeds through in situ generation of active hypervalent iodine(V) species 100 which facilitates the oxidation of substrates 97. This reaction occurs at room temperature under mild conditions without using any toxic heavy metals and desired products were isolated in significant yields.…”

Divergent synthesis of (+)-tanikolide and its analogues employing stereoselective rhodium(II)-catalyzed reaction

“…Reduction of ketone 6 could afford the alcohol 8 (R 2 = OR 4 ), which should be converted into 2 in the same manner as that of 7 into 1. Noranalogue 3 could be synthesized from 7 by an oxidative cleavage reaction 22 and cross metathesis. Consequently, in this synthesis, the C5 hydroxymethyl group plays the following important roles: construction of the C2 chiral center, ring-expansion from γlactone to δ-lactone, and oxidative cleavage.…”

“…To avoid these drawbacks, we recently developed an environmentally benign method for oxidative cleavage using a 2-iodobenzamide catalyst 41. 22 Therefore, we examined the oxidative cleavage under our original conditions. The reaction of 40 with 30 mol% 41 and 5 equivalent of Oxone in DMF at room temperature provided the corresponding γ-lactone 42 in 65% yield; however, unexpectedly, benzoate 43 was obtained in 12% yield.…”

Synthesis of 3-Substituted 2,1-Benzisoxazoles by the Oxidative Cyclization of 2-Aminoacylbenzenes with Oxone

“…Very likely, under our reaction conditions, the iodo-2-aminoacylbenzene derivatives 1n,o can be oxidized by Oxone to give iodine(V) species, which trigger further unselective oxidative processes. 34 In summary, we have developed a novel protocol for the synthesis of 2,1-benzisoxazoles via the oxidative cyclization reaction of 2-aminoacylbenzenes with Oxone. Such more environmentally friendly protocols, which utilize transition-metal-free, mild reaction conditions, and inexpensive and readily available reagents, provide an effective alternative strategy for the chemoselective construction of these target molecules, which occupy privileged positions in the fields of pharmaceuticals and materials science.…”