Sm(II)-Mediated Reduction in Water: Importance of the Additive in the Proportionation of SmCl₃ and Sm

REFERENCES

• For general reviews for Sm(II) chemistry, see (a) Molander , D. A. ; Harris , C. R. Sequencing reactions with samarium(II) iodide . Chem. Rev. 1996 , 96 , 307 – 338 ; (b) Kagan , H. B. Twenty-five years of organic chemistry with diiodosamarium: An overview . Tetrahedron 2003 , 59 , 10351 – 10372 ; (c) Edmond , D. J. ; Johnson , D. ; Procter , D. J. Samarium(II)-iodide-mediated cyclizations in natural product synthesis . Chem. Rev. 2004 , 104 , 3371 – 3374 .
   PubMed Web of Science ®Google Scholar
• (a) Otsubo , K. ; Inanaga , J. ; Yamaguchi , M. SmI2-induced cross-coupling of carbonyl compounds with α,β-unsaturated esters . Tetrahedron Lett. 1986 , 27 , 5763 – 5764 ; (b) Inanaga , J. ; Ishikawa , M. ; Yamaguchi , M. A mild and convenient method for the reduction of organic halides by using SmI2–THF solution in the presence of hexamethylphophoric triemide (HMPA) . Chem. Lett. 1987 , 1485 – 1486 ; (c) Kamochi , Y. ; Kudo , T. Reduction using samarium diiodide–base system . Tetrahedron Lett. 1991 , 32 , 3511 – 3514 ; (d) Inanaga , J. ; Sakai , S. ; Handa , Y. ; Yamaguchi , M. ; Yokoyama , Y. Selective conjugate reduction of α,β-unsaturated esters and amines via SmI2-promoted electron transfer process . Chem. Lett. 1991 , 2117 – 2118 ; (e) Mukhopadhyay , T. ; Seebach , D. Substitution of HMPT by the cyclic urea DMPU as a cosolvent for highly reactive nucleophiles and bases . Helv. Chim. Acta 1992 , 65 , 385 – 395 ; (f) Hasegawa , E. ; Curran , D. P. Additive and solvent effect on SmI2 reductions: The effect of water and DMPU . J. Org. Chem. 1993 , 58 , 5008 – 5010 ; (g) Kamochi , Y. ; Kudo , T. Novel reduction of carboxylic acids, esters, amides, nitriles using samarium diiodide in the presence of water . Chem. Lett. 1993 , 1495 – 1498 ; (h) Cabri , W. ; Candiani , I. ; Colombo , M. ; Franzoi , L. ; Bedeschi , A. Non-toxic ligands in samarium diiodide–mediated cyclizations . Tetrahedron Lett. 1995 , 36 , 949 – 952 ; (i) Dahlén , A. ; Hilmersson , G. Instantaneous SmI2-H2O-mediated reduction of dialkyl ketones induced by amines in THF . Tetrahedron Lett. 2002 , 43 , 7197 ; (j) Dahlén , A. ; Hilmersson , G. ; Knettle , B. W. ; Flowers , R. A. II . Rapid SmI2-mediated reductions of alkyl halides and electrochemical properties of SmI2/H2O/amine . J. Org. Chem. 2003 , 68 , 4870 – 4875 .
   Google Scholar
• Flowers , R. A. II . Mechanistic studies on the roles of cosolvents and additives in samarium(II)-based reductions . Synlett 2008 , 1427 – 1439 , and references are cited therein .
   Google Scholar
• For representative reviews for organic reactions in water, see (a) Li , C.-J. Organic reactions in aqueous media, with a focus on carbon–carbon bond formation . Chem. Rev. 1993 , 93 , 2023 – 2035 ; (b) Lindstrm , U. M. Stereoselective organic reactions in water . Chem. Rev. 2002 , 102 , 2751 – 2772 ; (c) Kobayashi , S. ; Manabe , K. Development of novel Lewis acid catalysis for selective organic reactions in aqueous media . Acc. Chem. Res. 2002 , 35 , 209 – 217 ; (d) Li , C.-J. Organic reactions in aqueous media with a focus on carbon–carbon bond formations: A decade update . Chem. Rev. 2005 , 105 , 3095 – 3166 .
   Web of Science ®Google Scholar
• (a) Wang , L. ; Zhang , Y. Novel reductive coupling cyclization of 1,1-dicyanoalkenes promoted by metallic samarium in aqueous media . Tetrahedron Lett. 1998 , 39 , 5257 – 5260 ; (b) Talukdar , S. ; Fang , J.-M. Reductive coupling reactions of carbonyl compounds using samarium metal in aqueous media . J. Org. Chem. 2001 , 66 , 330 – 332 ; (c) Liu , X. ; Liu , Y. ; Zhang , Y. A novel method for the synthesis of vicinal disulfonamides promoted by metallic samarium in aqueous media . Tetrahedron Lett. 2002 , 43 , 6787 – 6789 .
   Web of Science ®Google Scholar
• Matsukawa , S. ; Hinakubo , Y. Samarium(II)-mediated pinacol coupling in water: Occurrence of unexpected disproportionation and action of low-valent samarium as an active species . Org. Lett. 2003 , 5 , 1221 – 1223 .
   PubMed Web of Science ®Google Scholar
• For UV-vis studies of SmI2 and additives, see (a) Miller , R. S. ; Sealy , J. M. ; Shabangi , M. ; Kuhlman , M. L. ; Fuchs , J. R. ; Flowers , R. A. II . Reactions of SmI2 with alkyl halides and ketones: Inner-sphere vs outer sphere electron transfer in reactions of Sm(II) reductants . J. Am. Chem. Soc. 2000 , 122 , 7718 – 7722 ; (b) Prasad , E. ; Flowers , R. A. II . Mechanistic impact of water addition to SmI2: Consequences in the ground and transition state . J. Am. Chem. Soc. 2005 , 127 , 18093 – 18099 .
   Google Scholar
• (a) Keck , G. E. ; Wager , C. A. ; Sell , T. ; Wager , T. T. An especially convenient stereoselective reduction of β-hydroxy ketones to anti-1,3 diols using samarium diiodide . J. Org. Chem. 1999 , 64 , 2172 – 2173 ; (b) Chopade , P. R. ; Davis , T. A. ; Prasad , E. ; Flowers , R. A. II . Solvent-dependent diastereoselectivitys in reductions of β-hydroxyketones by SmI2 . Org. Lett. 2004 , 6 , 2685 – 2688 ; (c) Davis , T. A. ; Chopade , P. R. ; Hilmersson , G. ; Flowers , R. A. II . Reduction of β-hydroxyketones by SmI2/H2O/Et3N . Org. Lett. 2005 , 7 , 119 – 122 .
   Web of Science ®Google Scholar