Mild Cobalt-Catalyzed Hydrocyanation of Olefins with Tosyl Cyanide

Transcription

1 Mild Cobalt-Catalyzed ydrocyanation of lefins with Tosyl Cyanide Ts Co cat., Si 3 Et, 1-3 h, T Gaspar, B.; Carreira, E. M. Angew. Chem. Int. Ed. ASAP Current Literature Kalyani Patil 12 May 2007

2 utline i-catalyzed ydrocyanation Co-Catalyzed ydrohydrazination/ydroazidation Title Paper Summary

3 i-catalyzed Asymmetric ydrocyanation of lefins ArC C 2 + i(cd) 2/L ArC(C 3 ) Substrate ee(%) a b c d Me Ar 2 P Ar 2 P Ar = F 3 C CF 3 F F 3 C C 3 a b c d ajanbabu, T. V. et. al. J. Am. Chem. Soc. 1994, 116, 9869.

4 i-catalyzed ydrocyanation of lefins ajanbabu, T. V. et. al. J. Am. Chem. Soc. 1994, 116, 9869.

5 Co-Catalyzed ydration of lefins Co(acac) 2 i-pr 46% 8% 17% L 2 Co(III) Co(III)L 2 + Yamada, T. et. al. Bull. Chem. Soc. Jpn. 1990, 63, 179.

6 Co-Catalyzed ydrohydrazination of lefins a Co Si 3, Et, T, 2-8 h 6 mol% entry Alkene Products Br CEt CEt 66 Br Yield(%) dr > 5:1 Waser, J.; Carreira, E. M. J. Am. Chem. Soc. 2004, 126, Compatibility: monosubs, 1,1- and 1,2-disubs. trisubs. olefins primary Br and ketones styrene derivatives Limitations: tetrasubs. olefins cyclohexene crotyl alcohol

7 Mechanism for Co-Catalyzed ydrohydrazination Carreira, E. M. et. al. J. Am. Chem. Soc. 2006, 128,

8 Mn-Catalyzed ydrohydrazination of lefins 4 Mn mol% Si 3, i-pr, 0 C, 2-3 h Entry Alkene Products Yield(%) Advantages: broad range of substrates Faster reaction rates cheap PMS reductant 4 79 Waser, J.; Carreira, E. M. Angew. Chem. Int. Ed , 4099.

9 Co-Catalyzed ydrohydrazination of Dienes and Enynes mol% 2 L Co silane, Et, T entry diene products yield(%) Ts Ts 90 4 PMBz PMBz 61 5 Me 3 Si Me 2 C Me 3 Si C 2 Me 47 Carreira, E. M. et. al. rg. Lett. 2005, 7, 4249.

10 Co-Catalyzed ydroazidation of lefins t-bu C 2 K t-bu 6 mol% 1 + Ts mol% Co(BF 2 4 ) mol% t-bu, silane, Et, T 2-24 h entry Alkene Products Yield(%) Yield(%) with with 3 Si 3 TMDS t-busi Bn 2 t-busi Bn t-busi 73 2 t-busi dr = 4:1 dr = 4: Compatibility: Aromatic ring in allylic or homoallylic posn. Si protected allylic and homoallylic ethers Esters and ketones Geminally disubs. and trisubs. olefins with Si 3 Limitations: Styrene derivatives Free alcohols Carreira, E. M. et. al. J. Am. Chem. Soc. 2005, 127, 8294.

11 Catalytic Cycle for Co-Catalyzed ydroazidation Carreira, E. M. et. al. J. Am. Chem. Soc. 2006, 128,

12 Title Paper - Co-Catalyzed ydrocyanation of lefins TBDPS Me + Ts Co cat., Si 3 Et, T Me TBDPS Me 2 L Co t-bu t-bu Co L n t-bu Co X t-bu t-bu t-bu Co 1 = -(C 2 ) 4 -; X = Ac 2 = t-bu = ; no X = Gaspar, B.; Carreira, E. M. Angew. Chem. Int. Ed. 2007, 46, ASAP.

13 Title Paper - Co-Catalyzed ydrocyanation of lefins Entry Alkene Products Yield(%) Yield(%) TBDPS TBDPS TBDPS TBDPS 88 5 Et Et C C Conditions: catalyst 1 (1 mol%), alkene (0.5 mmol), Ts (0.75 mmol), tbu (30 mol%), Si 3 (0.5 mmol), Et (3 ml), argon, 23 C catalyst 2 (1 mol%), alkene (0.5 mmol), Ts (0.6 mmol), Si 3 (0.5 mmol), Et (2.5 ml), argon, 23 C

14 Title Paper - Co-Catalyzed ydrocyanation of lefins Entry Alkene Products Yield(%) Yield(%) TBDPS TBDPS C a a Compatibility: Simple alkenes, protected alcohols, esters and amides 2 works better for aldehydes, ketones, and tri-subs. alkenes Limitations: Styrene derivatives - moderate yield α,β-unsatd. Esters, cyclohexene b 81 c Conditions: catalyst 1 (1 mol%), alkene (0.5 mmol), Ts (0.75 mmol), tbu (30 mol%), Si 3 (0.5 mmol), Et (3 ml), argon, 23 C catalyst 2 (1 mol%), alkene (0.5 mmol), Ts (0.6 mmol), Si 3 (0.5 mmol), Et (2.5 ml), argon, 23 C [a] dr could not be determined. [b] dr = 17:1 [c] dr = 3:1 Gaspar, B.; Carreira, E. M. Angew. Chem. Int. Ed. 2007, 46, ASAP.

15 Summary Synthesis of secondary and tertiary nitriles by Co catalyzed hydrocyanation of olefins Broad substrate scope Mild reaction conditions eadily available starting materials