Asymmetric Photochemistry

Transcription

1 PSS, 2006, CCME Asymmetric otochemistry Reporter: Yong Liang Supervisor: Zhi-Xiang Yu 2006, 12, 8 1 Content Direct Asymmetric otochemistry with Circularly Polarized Light Diastereoseletive otoreactions with Chiral Auxiliaries Template Induced Enantioselective otochemical Reactions Enantioselective otoreactions with Chiral otosensitizers Summary and utlook Acknowledgement 2 1

2 Direct Asymmetric otochemistry with Circularly Polarized Light Background Examples 3 Linearly Polarized Light and Circularly Polarized Light (CPL) 4 2

3 ptical Rotatory Dispersion (RD) and Circular Dichroism (CD) Both RD and CD are wavelength dependent. RD is related to Δn = n l-cpl n r-cpl. CD is related to Δε = ε l-cpl ε r-cpl. Generally, Δn and Δε are small differences of large numbers. RD is measured by the rotation of the polarization plane of LPL that is tied directly to Δn. For CD, the two absorbances of one enantiomer versus l-cpl and r-cpl have to be measured separately. 5 CD Spectra 6 3

4 Anisotropy Factor g g Δε εl ε r = = ε ( ε ε )/2 l r Anisotropy factor g is wavelength dependent. g ranges between 0 and 2. For symmetry reasons, ε S = ε Δε/2 and ε R = ε Δε/2. For the same circularly polarized light, Δε = ε S ε R and ε = (ε R ε S )/2. 7 Direct Asymmetric otochemistry with Circularly Polarized Light Background Examples 8 4

5 Early Development In the pioneering paper of Le Bel in 1874, it was inferred that asymmetric induction could be caused by CPL. This possibility was definitely stated by van t off in The detection of CD by Cotton in 1896 further corroborated that CPL could induce optical activity in chemical systems. owever, it was not until 1929 that the first successful asymmetric photoreactions were found by W. Kuhn. C 3 C Br C C 2 5 C 3 C The interest in CPL induced photochemistry peaked again in the 1970s, when reliable spectropolarimeters for CD measurements became commercially available. 3 C (C 3 ) 2 40% conversion r CPL: 0.78 o l CPL: 1.04 o g: Asymmetric otodestruction CPL 345nm 2 59% conversion: 4.3% ee 83% conversion: 8.4% ee g: ~0.1 Blume, R.; Rau,.; Schuster,. J. Am. Chem. Soc. 1976, 98, CPL 313nm 60% conversion: 3.0% ee g: 0.15 icoud, J. F.; Eskenazi, C.; Kagan,. B. J. rg. Chem. 1977, 42,

6 Relationship between Conversion, ee and g in Asymmetric otodestruction d S hv d S* P l S hv l S* P g y 2 g 1 1 y 1 x = 1 [( ) ( ) ] 2 1 y 1 y [ R] [ S] [ R] [ S] x = 1 ( conversion); y = ( ee). [ R ] [ S ] [ R] [ S] 11 y Balavoine, G.; Moradpour, A.; Kagan,. B. J. Am. Chem. Soc. 1974, 96, x 12 6

7 C 3 C 3 C (C 3 ) 2 g = (λ = 280nm) g = (λ = 310nm) x = 40%, ee = 0.5% g = ee value, % x, % Calcd bsd , , 0.60 Balavoine, G.; Moradpour, A.; Kagan,. B. J. Am. Chem. Soc. 1974, 96, CPL 313nm 99% conversion: 30% ee g: 0.24 icoud, J. F.; Eskenazi, C.; Kagan,. B. J. rg. Chem. 1977, 42, Focused Laser Induced Enantioenrichment C C C C D tartaric acid r CPL 351nm 2hv C 2, C x = 13.9% ee = 7.5% C C C C racemic tartaric acid l CPL 351nm 2hv C 2, C x = 19.6% ee = 10.9% C C C C L tartaric acid ighly intense CPL is from an XeF (351nm) excimer laser. Shimizu, Y. J. Chem. Soc. Perkin Trans , racemic tartaric acid CPL >200nm conversion: >20% ee = 0.11% Mixed CPL is from an Xe lamp as continuous low-intensity light. orden, B. ature 1977, 266,

8 otoderacemization d S l S hv hv d S* l S* g ee = 100% 2 Balavoine, G.; Moradpour, A.; Kagan,. B. J. Am. Chem. Soc. 1974, 96, CPL 313nm g = ee = 1.6% Zhang, Y.; Schuster, G. B. J. rg. Chem. 1995, 60, Amplification of Chirality by Asymmetric Autocatalysis Extremely low ee (ca % ee) Asymmetric autocatalysis with significant amplification of ee C i Pr 2 Zn Extremely high ee (>99.5% ee) Sato, I.; Urabe,.; Ishiguro, S.; Shibata, T.; Soai, K. Angew. Chem. Int. Ed. 2003, 42,

9 Sato, I.; Urabe,.; Ishiguro, S.; Shibata, T.; Soai, K. Angew. Chem. Int. Ed. 2003, 42, Amplification of Small CPL Induced Enantiomeric Excesses l CPL (ca. 1.6% ee) r CPL C R R R (S > 90% ee) i Pr 2 Zn (R > 90% ee) R = t Bu Sato, I.; Sugie, R.; Matsueda, Y.; Furumura, Y.; Soai, K. Angew. Chem. Int. Ed. 2004, 43,

10 CPL 313nm g = x = 10% Calcd ee = 0.005% Kawasaki, T.; Sato, M.; Ishiguro, S.; Saito, T.; Morishita, Y.; Sato, I.; ishino,.; Inoue, Y.; Soai, K. J. Am. Chem. Soc. 2005, 127, l CPL r CPL R (ca % ee) C R R R i Pr (S > 99.5% ee) 2 Zn (R > 99.5% ee) R = t Bu Kawasaki, T.; Sato, M.; Ishiguro, S.; Saito, T.; Morishita, Y.; Sato, I.; ishino,.; Inoue, Y.; Soai, K. J. Am. Chem. Soc. 2005, 127,

11 CPL as a Source of omochirality in ature C 3 C 2 C(C 3 ) 2 D, (R) 2.5% ee l CPL x = 75% 3 C C 2 C 3 C C 3 C Leu in 0.1M Cl g = (λ = 213nm) r CPL x = 59% C 3 C 2 C(C 3 ) 2 L, (S) 2.0% ee Flores, J. J.; Bonner, W. A.; Massey, G. A. J. Am. Chem. Soc. 1977, 99, C 2 C 3 3 C C 2 C 3 L, (2S,3S) 7.0% ee C 2 C 3 C 3 C 2 C 3 L, (2S,3R) 9.1% ee C 2 C 3 C 2 C 3 L, (S) 8.4% ee C 2 C 3 (C 2 ) 2 C 3 L, (S) 2.8% ee Amino Acid from the Murchison Meteorite (4.5 billion years ago) Cronin, J. R.; Pizzarello, S. Science 1997, 275, Diastereoseletive otoreactions with Chiral Auxiliaries 22 11

12 Diastereoselective (62) otocycloaddition X hv X X X de, % hv (1R,2S,5R)-( )-menthol (S)-( )-1-phenylethylamine (2R,5R)-( )-2,5-dimethylpyrrolidine (7R)-()-camphorsultam X Wagner, P. J.; McMahon, K. J. Am. Chem. Soc. 1994, 116, Diastereoselective Radical Addition of Tertiary Amines to Electron-Deficient Alkenes hv 42% 52% ()-laburnine ( )-isoretronecanol Bertrand, S.; offmann,.; Pete, J. Eur. J. rg. Chem. 2000,

13 hv R* R* R* Bertrand, S.; offmann,.; Pete, J. Eur. J. rg. Chem. 2000, trans cis TS trans R* TS cis R* Bertrand, S.; offmann,.; Pete, J. Eur. J. rg. Chem. 2000,

14 Template Induced Enantioselective otochemical Reactions 27 Derivative of Tartaric Acid as Template Me (R,R) ( ) Me 1 equiv. (S,S,S,S) ( ) hv / cyclohexane 85% ee Me (R,R) ( ) 1 equiv. hv / cyclohexane (S,S,S,S) () Me 95% ee Me Tanaka, K.; Fujiwara, T. rg. Lett. 2005, 7,

15 Derivative of Lactam as Template Chiral Lactam Template Complex of Substrate and Chiral Lactam Template ent CLT 2.6 equiv. hv / 60 o C, C 3 > 90% ee 29 C2 Ac Me CLT Me C 2 Ac 2.4 equiv. hv / 60 o C, C 3 92% ee Me Et Et CLT 2.4 equiv. hv / 60 o C, C 3 Et Et Me 92% ee Bach, T.; Bergmann,.; Grosch, B.; arms, K. J. Am. Chem. Soc. 2002, 124,

16 K a Template Substrate {Substrate/Template} hv no enantioselectivity hv perfect enantioselectivity c({s/t}) c(s) / 2 c(s) / 2 c({s/t}) ee = = c({s/t}) c(s) c({s/t}) c(s) ee Kc(T) c(s) Kc a (T) Kc(T) c(s) c(s) Kc(T) 1 a = = a a 31 Enantioselective otoreactions with Chiral otosensitizers 32 16

17 Unimolecular otosensitized Reactions 6.7% ee hv / Sens* benzene ammond, G. S.; Cole, R. S. J. Am. Chem. Soc. 1965, 87, Sens*: Ac 0.12 equiv. Sens*: 10.4% ee hv / Sens* pentane *R 2 C C 2 R* *R 2 C C 2 R* R* = ( ) menthyl 0.17 equiv. Inoue, Y.; Yamasaki,.; Shimoyama,.; Tai, A. J. rg. Chem. 1993, 58, Z hv / Sens* 80 o C, hexane (S,S) (R) E (R,R) s 4 (S) E (S,S) Sens*: *R 2 C C 2 R* (R,R) *R 2 C C 2 R* R* = ( ) bornyl ( ) bornyl 0.20 equiv. 77% ee on an analytical scale offmann, R.; Inoue, Y. J. Am. Chem. Soc. 1999, 121,

18 Bimolecular otosensitized Reactions hv / Sens* 65 o C, toluene Sens*: X C X X ee, % C C C 3 F C Kim, J.; Schuster, G. B. J. Am. Chem. Soc. 1992, 114, R 1 R 2 hv Sens* R 1 * R 2 R 1 = Me, Et R 2 = Me, Et, i Pr Sens*: *R 2 C C 2 R* Best ee: 58% Sens*: 0.15 equiv. Product yield: 1% R*: R 1 = Me, R 2 = i Pr 0 o C, Et 2 over 50 Sens*, about 500 reactions Asaoka, S.; Wada, T.; Inoue, Y. J. Am. Chem. Soc. 2003, 125,

19 Summary and utlook Part 1. Direct Asymmetric otochemistry with Circularly Polarized Light Important in Theory Part 2. Diastereoseletive otoreactions with Chiral Auxiliaries Important in Synthesis Part 3. Template Induced Enantioselective otochemical Reactions Stoichiometric / Practical Part 4. Enantioselective otoreactions with Chiral otosensitizers Catalytic / Unpractical 37 ther Fields in Asymmetric otochemistry Chiral otochemistry with Transition Metal Complexes Absolute Asymmetric otochemistry Using Spontaneous Chiral Crystallization The Solid-State Ionic Chiral Auxiliary Approach to Asymmetric Induction in otochemistry Supramolecular Asymmetric Solid-State otochemistry Scheffer, J. R.; Xia, W. Top. Curr. Chem. 2005, 254,

20 A Wonderful Story hv 42% 52% Bertrand, S.; offmann,.; Pete, J. Eur. J. rg. Chem. 2000, ent CLT 2.6 equiv. hv / 60 o C, C 3 > 90% ee Bach, T.; Bergmann,.; Grosch, B.; arms, K. J. Am. Chem. Soc. 2002, 124, equiv. hv / 60 o C, C 3 (R,R) (S,S) CLT 1.2 equiv. (R,R) 72% ee Bauer, A.; Westkamper, F.; Grimme, S.; Bach, T. ature 2005, 436,

21 Seminal Work in Catalytic Asymmetric otochemistry Bauer, A.; Westkamper, F.; Grimme, S.; Bach, T. ature 2005, 436, A Breakthrough in Chiral otochemistry!!! Yoshihisa Inoue Catalyst 0.1 equiv. (R,R) 38% ee 52% yield ent Catalyst 0.1 equiv. 0.2 equiv. 0.3 equiv. ee, % yield, % (S,S) Bauer, A.; Westkamper, F.; Grimme, S.; Bach, T. ature 2005, 436,

22 R* R* Bauer, A.; Westkamper, F.; Grimme, S.; Bach, T. ature 2005, 436, Catalyst (R,R) (S,S) ent Catalyst ow to obtain (R,S) or (S,R)? Stereochemical Control in rganic Synthesis reported by Lei Jiao 44 22

23 Acknowledgement Professor Zhi-Xiang Yu All Professors in the Institute of rganic Chemistry My Labmates: Graduate Postdoctor Feng uang Fuqiang Shi Xin Li Lei Jiao Yuanyuan Chen Yuanyuan Wang Siyu Ye Yuanzhi Xia Xiaohui Fan Undergraduate Song Liu Yang Luo Yang Zhou 45 Thanks for Attention! 46 23

24 Total Synthesis of () Laburnine ab 4 Me 83% hv, DC 2, LiCl 4 LiAl 4 ()-laburnine 81% 78% Bertrand, S.; offmann,.; Pete, J. Eur. J. rg. Chem. 2000, Kawasaki, T.; Sato, M.; Ishiguro, S.; Saito, T.; Morishita, Y.; Sato, I.; ishino,.; Inoue, Y.; Soai, K. J. Am. Chem. Soc. 2005, 127,