Stereoselective construction of anti - and syn -1,2-diol structures via decarbonylative radical coupling of α-alkoxyacyl tellurides

Reaction of arylhydrazines with diaryl ditellurides in the air: Insight into bimolecular homolytic substitution on tellurium via Aryl–Te bond cleavage

“…Organotellurium compounds have served as important synthetic intermediates, and especially, diorganyl tellurides have been used as carbon nucleophile sources through a tellurium‐lithium exchange reaction . In addition, a relatively weaker carbon–tellurium bond (48 kcal/mol) makes organotellurium compounds fascinating in radical chemistry .…”

Unified Total Synthesis of Polyoxins J, L, and Fluorinated Analogues on the Basis of Decarbonylative Radical Coupling Reactions

“…2:1a tC5). [11,12] Thec ompatibility of the preinstalled nucleobases with the reaction conditions was unknown at this stage, [13,14] but we expected that direct attachment of the a-amino acid portion to 5a-d would streamline the route to 1a-d.…”

“…Ther adical-exchange reaction between 5a-d/6 and the ethyl radical generated from Et 3 Band O 2 provides the corresponding a-alkoxyacyl radical Aa-d/C.N ext, favorable orbital interactions of the C À CO s*-bond of Aa-d/C with the antiperiplanar oxygen lone pair facilitates ejection of CO to generate Ba-d/D. [11,12,22] Thel ost stereochemical information at the C4' or C3'' position of Ba-d/D is redefined by CÀC bond formation. Thea cetonide methyl group of the 5/5-cisfused bicycle Ba-d,and the siloxymethyl group of monocycle D,block the corresponding top and bottom faces,respectively, thus forcing the approach of oxime 4 from the opposite faces to establish the C4' and C3'' stereocenters.…”

Unified Total Synthesis of Polyoxins J, L, and Fluorinated Analogues on the Basis of Decarbonylative Radical Coupling Reactions

“…To simplify the synthetic scheme and minimize functional-group transformations,w e decided to extend the multiply functionalized chains of 1a-d from readily accessible ribonucleosides 5a-d containing four different nonprotected pyrimidine rings. [11,12] Thec ompatibility of the preinstalled nucleobases with the reaction conditions was unknown at this stage, [13,14] but we expected that direct attachment of the a-amino acid portion to 5a-d would streamline the route to 1a-d. [10] We recently reported that a-alkoxyacyl telluride 7 and oxime 8 were smoothly assembled into the ribonofuranosyl a-amino acid 9 through Et 3 B/O 2 -promoted decarbonylative radical addition, albeit with low C5 stereoselectivity (d.r.…”

“…[20] Despite the differences in the C5 substituents on the pyrimidine rings,E t 3 B/O 2 -promoted reactions of 5b, 5c, and 5d successfully attached the a-amino acid structure to yield 2b (64 %), 2c (69 %), and 2d (64 %) in ad iastereoselective fashion with respect to the formation of the C4' and C5' centers.T he same procedure was applied to 6 and 4 (2 equiv) to produce the protected trihydroxynorvaline fragment 3 with complete control of the newly formed C2'',C3'' stereocenters.T hus, 2a-d and 3 were prepared in only four steps from the starting materials 10 a-d and 12,respectively. [11,12,22] Thel ost stereochemical information at the C4' or C3'' position of Ba-d/D is redefined by CÀC bond formation. Ther adical-exchange reaction between 5a-d/6 and the ethyl radical generated from Et 3 Band O 2 provides the corresponding a-alkoxyacyl radical Aa-d/C.N ext, favorable orbital interactions of the C À CO s*-bond of Aa-d/C with the antiperiplanar oxygen lone pair facilitates ejection of CO to generate Ba-d/D.…”