Samarium diiodide-induced reductive coupling of chiral nitrones with methyl acrylate

Abstract

D-Lyxose derived nitrone 7 was found to effectively undergo an SmI 2 -mediated radical addition to methyl acrylate affording γ-N-hydroxylamino ester 8 with high diastereomeric control. The pyrrolidinone 9 was prepared in a single step from 8 involving N-O bond cleavage with Zn/AcOH and subsequent spontaneous cyclization. D-Xylose derived nitrone 10 afforded in the SmI 2 -induced coupling with methyl acrylate the γ-N-hydroxylamino ester 11 as minor product. The major product the nitrone 12 is formed by unusual reductive deoxygenation of the starting nitrone.

Samarium Diiodide Induced Reductive Coupling of d-Threose- and d-Erythrose-Derived Nitrones with Methyl Acrylate

“…Scheme 5 Samarium diiodide promoted coupling between TB-DMS-substituted D-erythro-nitrone 11 and methyl acrylate As has been mentioned in our previous communication, we have found that the reaction course of samarium diiodide induced reductive coupling of chiral nitrones with methyl acrylate is dependent on the structure of the starting chiral nitrone. 7 The results obtained using diastereomeric D-threo-nitrones 8, 9 and D-erythro-nitrones 10, 11 support this observation. In both cases the coupling of the nitrones 5, 10, and 11 possessing a C2/C3 erythro config-Scheme 3 Samarium diiodide promoted coupling betweenTBDMSsubstituted D-threo-nitrone 9 and methyl acrylate…”

“…The major product, nitrone 7, is formed by unusual reductive deoxygenation of the starting nitrone (Scheme 1). 7 In this communication we wish to describe the SmI 2 -induced coupling of readily available chiral sugar D-threose-and D-erythrose-derived nitrones 8, 9 and 10, 11 to methyl acrylate with the subsequent conversion of the formed g-N-hydroxylamino esters into g-lactams.…”

“…This kind of reductive cleavage of the starting a-alkoxysubstituted nitrone 11, producing nitrone 24 by SmI 2 -induced reduction, was previously observed in the formation of nitrone 7 from nitrone 5 (Scheme 1). 7 The origin of the further unexpected b-N-hydroxylamino alcohol 25 can be explained by the coupling of the starting nitrone 11 with in situ formed acetaldehyde by aforementioned deoxygenation of nitrone 11. The formation of dimer 20 suggests that the C-C bond-forming reaction between Derythro-nitrone 11 and methyl acrylate is comparable with the radical dimerization-addition step involving the acrylate.…”