Iodide-Mediated Synthesis of Spirooxindolo dihydrofurans from Iodonium Ylides and 3-Alkylidene- 2-oxindoles

Transcription

1 Iodide-Mediated Synthesis of Spirooxindolo dihydrofurans from Iodonium Ylides and 3-Alkylidene- 2-oxindoles Benjamin A. Laevens, Jason Tao and Graham K. Murphy* Department of Chemistry, University of Waterloo, Waterloo,, Canada, 2L3G1 Table SI-1: ptimization of the Dihydrofuran Synthesis:... SI-1 Table SI-2: Control Experiments:... SI-3 MR Spectra Used for Structural Elucidation of 3a:... SI-4 Figure SI-1: RTEP representation (50% probability) of the crystal structure of 3a.... SI-7 1 H, 13 C and 19 F Spectra of ew Compounds... SI-8 Table SI-1: ptimization of the Dihydrofuran Synthesis: The reaction was optimized using alkylidene 1a and iodonium ylide 2a. a 1a Ac 2a entry solvent (0.1 M) temperature ( C) 2a (equiv) PhI(Ac) 2 (equiv) TBAI Time (hr) conv. b (%) Yield c 1 MeC rt MeC MeC MeC rt MeC rt IPh PhI(Ac) 2, Bu 4 I temperature, time solvent Ac 3a SI-1

2 6 MeC rt MeC rt MeC rt DCM rt DCM rt DCE rt Toluene rt DCM reflux MeC rt MeC rt MeC rt MeC rt MeC rt <5% 19 MeC rt MeC rt MeC rt MeC rt MeC rt MeC MeC MeC d rt MeC rt MeC MeC MeC b MeC b MeC b a Reaction Conditions: 1a (0.1 mmol) is combined with ylide 2a, PhI(Ac) 2 and Bu 4 I in solvent (0.1 M) and the reaction is stirred at the indicated temperature for the indicated length of time. b Conversions listed as >95% indicate that less than 5 mol% of 1a remained according to quantitative 1 H MR analysis. c Yield determined by 1 H MR, using hexamethyldisiloxane as internal standard. d Reaction concentration was 0.2 M. e Alkylidene 1e was used in these experiments. otes: Using the conditions previously reported, at various temperatures, the reaction worked well but the yields were moderate to good. (entries 1-3) Increasing the amount of ylide 2a had little effect on the reaction. We elected to optimize using equimolar ratio of 1a and 2a. (entries 1, 4-7) SI-2

3 Varying solvents showed MeC to be best, however the reaction could be accelerated with heating. (entries 8-13) Varying the loading of the PhI(Ac) 2 / Bu 4 I mixture resulted in similar conversions. (entries 14-17) Control experiments: the reaction workedvery well with only Bu 4 I. (entries 18-20) Varying the loading of Bu 4 I, and the temperature and concentration of MeC gave high yields and conversions. (entries 21-26) Increasing the loading of 2a gave complete conversion and high yields. Reactions at either 60 C or reflux were similar yielding, and occured in similar times. (entries 27-29) Testing the reactions with alkene 1e show the reactions at 60 C to be better (entries 30-31), and reacting 1e with 1.1 equiv of 2a gave 3e in 97% yield. Table SI-2: Control Experiments: The reaction was optimized using alkylidene 1e and oxonium ylide 2a. a IPh Bn 1e 2a iodide ( I ) additive 60 C, time CH 3 C 3e Bn entry I additive Time conv. b Yield c (equiv) (equiv) (hr) (%) 1 Bu 4 I (0.3) d d <5% - 5 I ai Bu 4 Br (0.3) Bu 4 Cl (0.3) Bu 4 I (0.3) BHT (0.3) Bu 4 I (0.3) DDQ (0.3) d Bu 4 I (0.3) DDQ (0.3) d - DDQ (0.3) a Reaction Conditions: 1e (0.1 mmol) is combined with 2a (1.1 equiv, 0. mmol), the iodine source ( I ) and the additive in CH 3 C (0.1 M) and the reaction is stirred at the indicated temperature for the indicated length of time. b Conversion and yield determined by 1 H MR, using hexamethyldisiloxane as internal standard. d Substrate 1e was omitted. Conversion refers to ylide (2a) consumption. SI-3

4 otes: The standard reaction (entry 1) fails without Bu 4 I (entry 2), which is consistent with the control experiments performed with susbstrate 1a (see Table SI-1, entries 18-19). The ylide is slightly decomposed (25% consumption) by Bu 4 I over 2 hours at 60 C, however the ylide alone is only slightly decomposed under these conditions (entries 3,4). ai could be used instead of Bu 4 I, but not I 2, and though Bu 4 Cl and Bu 4 Br could be used, the yields were greatly decreased (entries 5-8). Adding the radical inhibitor BHT failed to suppress the reaction, giving 3e in 95% yield (entry 9). Adding the radical inhibitor DDQ caused the reaction to fail, with only 13% of 3e produced (entry 10). Reacting 2a with Bu 4 I and DDQ resulted in complete decomposition of the ylide (entry ), and heating 2a with DDQ alone also resulted in 77% consumption of the ylide. It appears that 2a is being chemically degraded by DDQ under the reaction conditions, and that the result of entry 10 is a by-product thereof. MR Spectra Used for Structural Elucidation of 3a: SI-4

5 SI-5

6 SI-6

7 Figure SI-1: RTEP representation (50% probability) of the crystal structure of 3a. SI-7

8 1 H, 13 C and 19 F Spectra of ew Compounds SI-8

9 proton 16 scans Ac 3a, 91% ppm SI

10 C-13 proton Decoupled Ac 3a, 91% ppm SI

11 proton 16 scans CBZ 3b, 90% ppm SI

12 C-13 proton Decoupled 3b, 90% CBZ ppm SI

13 proton 16 scans Boc 3c, 99% ppm SI

14 C-13 proton Decoupled 3c, 99% Boc ppm SI

15 proton 16 scans 3d, 90% Ts ppm SI

16 C-13 proton Decoupled 3d, 90% Ts ppm SI

17 proton 16 scans 3e, 97% Bn ppm SI

18 C-13 proton Decoupled 3e, 97% Bn ppm SI

19 proton 16 scans allyl 3f, 85% ppm SI

20 C-13 proton Decoupled allyl 3f, 85% ppm SI

21 proton 16 scans Me 3g, 98% ppm SI

22 C-13 proton Decoupled Me 3g, 98% ppm SI

23 proton 16 scans F Ac 3h, 87% ppm SI

24 C-13 proton Decoupled F Ac 3h, 87% ppm SI

25 -4.73 F-19 bserved o H1 Decoupling referenced to TFA at ppm F Ac 3h, 87% ppm SI

26 proton 16 scans Cl Ac 3i, 84% ppm SI

27 C-13 proton Decoupled Cl Ac 3i, 84% ppm SI

28 proton 16 scans Br Ac 3j, 84% ppm SI

29 C-13 proton Decoupled Br Ac 3j, 84% ppm SI

30 proton 16 scans F Boc 3k, 73% ppm SI

31 C-13 proton Decoupled F Boc 3k, 73% ppm SI

32 -6.33 F-19 bserved o H1 Decoupling referenced to TFA at ppm F Boc 3k, 73% ppm SI

33 proton 16 scans Cl Boc 3l, 77% ppm SI

34 C-13 proton Decoupled Cl Boc 3l, 77% ppm SI

35 proton 16 scans Br Boc 3m, 76% ppm SI

36 C-13 proton Decoupled Br Boc 3m, 76% ppm SI

37 proton 16 scans Ph 3n, 99% Ac ppm SI

38 C-13 proton Decoupled Ph 3n, 99% Ac ppm SI

39 proton 16 scans 3o, 89% Ac ppm SI

40 C-13 proton Decoupled 3o, 89% Ac ppm SI

41 proton 16 scans Ph 3p, 82% Ac ppm SI

42 C-13 proton Decoupled ppm SI

43 proton 16 scans Ac 3q, 97% ppm SI

44 C-13 proton Decoupled Ac 3q, 97% ppm SI

45 proton 16 scans Ac 3s, 54% ppm SI

46 C-13 proton Decoupled Ac 3s, 54% ppm SI

47 proton 16 scans Ac 3t, 45% ppm SI

48 C-13 proton Decoupled Ac 3t, 45% ppm SI