Reductive Cleavage of the Se¡ÓSi Bond inArylselenotrimethylsilanes: Novel Method forthe Synthesis of Unsymmetrical Selenides$Songlin Zhang and Yongmin Zhang*Department of Chemistry, Hangzhou University, Hangzhou, 310028, P.R. ChinaArylselenotrimethylsilanes are reduced by samarium diiodide to yield samarium areneselenolates, which react with alkylhalides to give unsymmetrical selenides.As a powerful and versatile one-electron transfer reducingand coupling reagent, SmI2 has been applied widely inorganic synthesis.1¡Ó3 Our previous work on the reductivecleavage of S¡ÓS, Se¡ÓSe and Te¡ÓTe bonds with SmI24.5 ledus to investigate the reductive cleavage of Se¡ÓSi bonds bySmI2.Selenides are involved in important transformationssuch as the synthesis of alkanes,6¡Ó8 alkenes,9¡Ó11 and alkylhalides,12,13 but relatively few syntheses of selenides havebeen described. A useful approach to the synthesis ofselenides is based on the alkylation of selenide ion, whichcan easily be prepared from elemental selenium by reductionwith sodium in liquid ammonia,14 sodium tetrahydroboratein ethanol15 or water16 or with tetraalkylammonium tetra-hydroborates.17 In another approach, alcohols and selenolswere treated with acid to give selenides.18 Most of thesemethods have been applied successfully to the synthesis ofselenides.Here we report that SmI2 reduces arylselenotrimethyl-silanes to samarium areneselenolates under a nitrogen atmo-sphere.This new selenolate anion species reacts with alkylhalides to give unsymmetrical selenides in good yield underneutral conditions (Scheme 1).In summary, a novel method for the preparation ofunsymmetrical selenides has been elucidated, the advantagesof which are simple manipulation, mild and neutralconditions.ExperimentalGeneral Procedure.A solution of arylselenotrimethylsilane19(1 mmol) in THF (1 ml) was added by syringe to a deep bluesolution of SmI2 (2.2 mmol) in THF (10 ml) at reux temperatureunder a nitrogen atmosphere.The deep blue solution graduallybecame brown within 3 h, which showed that the Se¡ÓSi bond hadbeen reductively cleaved by SmI2 and that the samarium arene-selenolate (ArSeSmI2)20 had been generated. Alkyl halides (1 mmol)in THF (1 ml) were then added by syringe and stirred at reuxingtemperature for 3 h. A dilute solution of HCl and diethyl etherwas added. The organic layer was washed with water (20 ml2)and dried over anhydrous Na2SO4. The solvent was removedin vacuo.The crude product was puried by preparative TLC onsilica gel (cyclohexane as eluent). Some results are summarized inTable 1.1.20 mp 34¡Ó35 8C, dH (CCl4) 3.93 (2 H, s), 7.00¡Ó7.40 (10 H, m);~max/cm£¾1 3100, 3080, 3040, 2950, 1610, 1590, 1500, 1485, 1460,1440, 1180, 1080, 1020, 1000, 910, 760, 740, 660, 6002.21 Oil, dH (CCl4) 0.80 (3 H, t), 1.07¡Ó1.60 (12 H, m), 2.75 (2 H,t), 7.00¡Ó7.50 (5 H, m); ~max/cm£¾1 3100, 3080, 2980, 2980¡Ó2940,2870, 1590, 1485, 1460, 1440, 1380, 1075, 1020, 1000, 730, 690, 660.3.22 Oil, dH (CCl4) 0.80 (3 H, t), 1.07¡Ó1.57 (16 H, m), 2.77 (2 H,t), 7.00¡Ó7.60 (5 H, m); ~max/cm£¾1 3100, 3080, 2980, 2960¡Ó2940, 2870,1590, 1486, 1440, 1380, 1080, 1020, 1000, 730, 690, 665.4.10 Oil, dH (CCl4) 0.82 (3 H, t), 1.07¡Ó1.60 (20 H, m), 2.77 (2 H,t), 7.00¡Ó7.60 (5 H, m); ~max/cm£¾1 3100, 3080, 2980, 2960¡Ó2940,2870, 1590, 1485, 1470, 1440, 1380, 1080, 1020, 1000, 730, 690, 660.5.23 mp 33¡Ó34 8C, dH (CCl4) 0.80 (3 H, t), 1.07¡Ó1.60 (28 H, m),2.77 (2 H, t), 7.00¡Ó7.60 (5 H, m); ~max/cm£¾1 3100, 3080, 2980,2960¡Ó2940, 2870, 1590, 1485, 1470, 1440, 1075, 1020, 1000, 730,690, 665.6.24 Oil, dH (CCl4) 2.20 (3 H, s), 3.87 (2 H, s), 6.83¡Ó7.40 (9 H,m); ~max/cm£¾1 3100, 3080, 3040, 2990, 2950, 2870, 1600, 1500, 1470,1460, 1385, 1270, 1200, 1180, 1040, 820, 760, 690, 650, 600.7.25 Oil, dH (CCl4) 2.30 (3 H, s), 2.54 (3 H, s), 6.90¡Ó7.40 (4 H,m); ~max/cm£¾1 3100, 3080, 2980, 2950, 2870, 1595, 1485, 1470, 1440,1380, 1040, 735, 650.8.25 Oil, dH (CCl4) 1.30 (3 H, t), 2.30 (3 H, s), 2.73 (2 H, q),6.91¡Ó7.45 (4 H, m); ~max/cm£¾1 3100, 3080, 2980, 2960, 2870, 1590,1485, 1470, 1440, 1380, 1040, 730, 690, 660.9.25 Oil, dH (CCl4) 1.36 (6 H, d), 2.30 (3 H, s), 3.01¡Ó3.08 (1 H, m)6.90¡Ó7.40 (4 H, m); ~max/cm£¾1 3100, 3080, 2980¡Ó2960, 2870, 1590,1485, 1470, 1440, 1380, 1040, 730, 690, 665.1H NMR spectra were recorded on a PMX-60 MHZ instru-ment (TMS as internal reference), IR spectra on a PE-683 spec-trometer.J. Chem.Research (S),1998, 000¡Ó000$Scheme 1Table 1 Yields of the products ArSeREntry Ar R¡ÓX Product Yielda (%)a Ph PhCH2Clb 1 PhSeCH2Ph 84b Ph PhCH2Brb 1 PhSeCH2Ph 84c Ph CH3(CH2)7Br 2 PhSe(CH2)7CH3 80d Ph CH3(CH2)9Br 3 PhSe(CH2)9CH3 77e Ph CH3(CH2)11Br 4 PhSe(CH2)11CH3 79f Ph CH3(CH2)15Br 5 PhSe(CH2)15CH3 75g o-CH3C6H4 PhCH2Clb 6 o-CH3C6H4SeCH2Ph 82h o-CH3C6H4 PhCH2Brb 6 o-CH3C6H4SeCH2Ph 82i o-CH3C6H4 CH3I 7 o-CH3C6H4SeCH3 80j o-CH3C6H4 CH3CH2I 8 o-CH3C6H4SeCH2CH3 76k o-CH3C6H4 CH3CH(Br)CH3 9 o-CH3C6H4SeCH(CH3)2 68aOf isolated product. b Alkylation at room temperature for 4 h.We are grateful to the National Natural ScienceFoundation of China and Laboratory of OrganometallicChemistry, Shanghai Institute of Organic Chemistry,Chinese Academy of Sciences, for nancial support.$This is a Short Paper as dened in the Instructions for Authors,Section 5.0 [see J.Chem. Research (S), 1998, Issue 1]; there is there-fore no corresponding material in J.Chem. 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