Timeless Methods for Radical Cyclizations in Total Synthesis. Patricia Zhang MacMillan Group Meeting Wednesday September 25th, 2013
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1 Timeless thods for adical Cyclizations in Total Synthesis Patricia Zhang MacMillan Group eting Wednesday September 25th, 2013
2 ! A little history! 1900: Moses Gomberg "Ph 3 C" rather than "Ph 3 C " trivalent carbon (discovery predated electronic theory)! 1929: Paneth and ofeditz! in rapid current of 2 Pb(C 3 ) 4 Pb + 4C 3 Gomberg, M. J. Am. Chem. Soc. 1900, 22, 757. Paneth, F.; ofeditz, W. Chem. Ber. 1929, 62, 1335.
3 ! A change in the synthetic community's outlook on carbon radicals "Unruly & Uncontrollable"! dimerization at diffusion rates! disproportionation! polymerization! extremely reactive Functional Group Transformations! Kolbe oxidation! offman-loffler-freytag! erwein arylation! BS bromination! Kharasch reaction! Tin ydride then in the 1980s... "Mild, eutral and Selective"! extremely reactive! neutral species, good for crowded bonds! inert to and! no!-elimination of,, etc.! ground state of structures good T.S. models! easy racemic synthesis of radical precursor Synthetic adical Chemistry! Giese reactions: Intermolecular Additions! Barton's thiohydroxamates: Carbon adicals! art's pyrrolizidine synthesis! Stork's regio- and stereoselective syntheses! Curran's tandem syntheses Jasperse, C. P.; Curran, D. P.; Fevig, T. L. Chem. ev. 1991, 91,
4 ! Goal: General overview of major methods from the 1980s boom Cyclizations organized by method of radical generation: The Tin ydride thod The Fragmentation thod The eduction thod The xidation thod Showcase power of these methods with examples from today
5 ! The Tin ydride thod Bu 3 Sn, AIB,! X C C ' Initiation: C AIB C! 2 C + 2 C + Bu 3 Sn C + Bu 3 Sn Propagation: Bu 3 Sn + -X + Bu 3 SnX addition or + C C cyclization ' ' + Bu 3 Sn '- + Bu 3 Sn Jasperse, C. P.; Curran, D. P.; Fevig, T. L. Chem. ev. 1991, 91,
6 ! The Tin ydride thod Bu 3 Sn, AIB,! X C C ' Initiation: C AIB C! 2 C + 2 C + Bu 3 Sn C + Bu 3 Sn Propagation: Bu 3 Sn + -X + Bu 3 SnX addition or + C C cyclization ' ' + Bu 3 Sn '- + Bu 3 Sn Jasperse, C. P.; Curran, D. P.; Fevig, T. L. Chem. ev. 1991, 91,
7 ! The Tin ydride thod Bu 3 Sn, AIB,! X C C ' Initiation: C AIB C! 2 C + 2 C + Bu 3 Sn C + Bu 3 Sn Propagation: Bu 3 Sn + -X + Bu 3 SnX addition or + C C cyclization ' ' + Bu 3 Sn '- + Bu 3 Sn Jasperse, C. P.; Curran, D. P.; Fevig, T. L. Chem. ev. 1991, 91,
8 ! adical cyclizations follow Baldwin's rules X Bu 3 Sn, AIB,! C C C C Gilmore, K.; Alabugin, I. V. Chem. ev. 2011, 11,
9 ! adical cyclizations follow Baldwin's rules C X C Bu 3 Sn, AIB,! C C boxed structures are allowed Gilmore, K.; Alabugin, I. V. Chem. ev. 2011, 11,
10 ! The Tin ydride thod Bu 3 Sn, AIB,! X C C '! Bu 3 Sn most commonly used reagent to conduct free-radical reactions! verall reaction: -X for stronger -, Sn- for stronger Sn-X Substrate Trends:! Transferability of X to Bu 3 Sn is X + Bu 3 Sn Bu 3 Sn-X I > Br > SePh > "C(S)S > Cl > SPh! eactivity of to Bu 3 Sn is + Bu 3 Sn Bu 3 Sn + - aryl # vinyl > alkyl > allyl # benzyl Jasperse, C. P.; Curran, D. P.; Fevig, T. L. Chem. ev. 1991, 91,
11 ! The Tin ydride thod Bu 3 Sn, AIB,! X C C '! Bu 3 Sn most commonly used reagent to conduct free-radical reactions! verall reaction: -X for stronger -, Sn- for stronger Sn-X Substrate Trends:! Transferability of X to Bu 3 Sn is X + Bu 3 Sn Bu 3 Sn-X I > Br > SePh > "C(S)S > Cl > SPh! eactivity of to Bu 3 Sn is + Bu 3 Sn Bu 3 Sn + - aryl # vinyl > alkyl > allyl # benzyl Jasperse, C. P.; Curran, D. P.; Fevig, T. L. Chem. ev. 1991, 91,
12 ! The Tin ydride thod Bu 3 Sn, AIB,! X C C '! Bu 3 Sn most commonly used reagent to conduct free-radical reactions! verall reaction: -X for stronger -, Sn- for stronger Sn-X Substrate Trends:! Transferability of X to Bu 3 Sn is X + Bu 3 Sn Bu 3 Sn-X I > Br > SePh > "C(S)S > Cl > SPh! eactivity of to Bu 3 Sn is + Bu 3 Sn Bu 3 Sn + - aryl # vinyl > alkyl > allyl # benzyl Jasperse, C. P.; Curran, D. P.; Fevig, T. L. Chem. ev. 1991, 91,
13 ! Beckwith's rules! Cyclizations containing five linking carbons or less prefers exo-mode! adicals add to least substituted carbon of olefin if no other geometric constraints! Bond undergoing homolytic cleavage must lie close to the plane of the radical! 5-exenyl radical ring closures are stereoselective: , 4- substituted systems give trans ,3-, or 4- substitued systems reflects conformation preference of chair T.S. Jasperse, C. P.; Curran, D. P.; Fevig, T. L. Chem. ev. 1991, 91,
14 ! Beckwith's rules! Cyclizations containing five linking carbons or less prefers exo-mode! adicals add to least substituted carbon of olefin if no other geometric constraints! Bond undergoing homolytic cleavage must lie close to the plane of the radical! 5-exenyl radical ring closures are stereoselective: ,3- substituted systems give cis Jasperse, C. P.; Curran, D. P.; Fevig, T. L. Chem. ev. 1991, 91,
15 ! Beckwith's rules! Cyclizations containing five linking carbons or less prefers exo-mode! adicals add to least substituted carbon of olefin if no other geometric constraints! Bond undergoing homolytic cleavage must lie close to the plane of the radical! 5-exenyl radical ring closures are stereoselective: ,4- substituted systems give cis Jasperse, C. P.; Curran, D. P.; Fevig, T. L. Chem. ev. 1991, 91,
16 ! Beckwith's rules! Cyclizations containing five linking carbons or less prefers exo-mode! adicals add to least substituted carbon of olefin if no other geometric constraints! Bond undergoing homolytic cleavage must lie close to the plane of the radical! 5-exenyl radical ring closures are stereoselective: , 4- substituted systems give trans 2-,3-, or 4- substitued systems reflects conformation preference of chair T.S Jasperse, C. P.; Curran, D. P.; Fevig, T. L. Chem. ev. 1991, 91,
17 ! Carbacycle formation with tin hydride! Cyclizations yielding 5-membered rings are fast 20x faster! igh regioselectivity for 5-exo 50x faster + Jasperse, C. P.; Curran, D. P.; Fevig, T. L. Chem. ev. 1991, 91,
18 ! Carbacycle formation with tin hydride! Cyclizations yielding 5-membered rings are fast 20x faster! igh regioselectivity for 5-exo 50x faster + Jasperse, C. P.; Curran, D. P.; Fevig, T. L. Chem. ev. 1991, 91,
19 ! First application of tin hydride in total synthesis Br 6-exo 62% + 3 : 2! 6-membered rings are less general than 5! diminished regioselective and stereoselectivity! more suspectible to reduction before cyclization + 6x faster 1,5 hydrogen transfer sativene cocamphene Jasperse, C. P.; Curran, D. P.; Fevig, T. L. Chem. ev. 1991, 91, Bakuzi, P.; Campos,.. S.; Bakuzis, M. L. F. J. rg. Chem. 1976, 41,
20 ! Stork improves the 6-exo cyclization I Bu 3 Sn, UV irradiation 72% no 7-endo product 1 : 1 diastereomers! vinyl radicals much more reactive to cyclization! more suspectible to reduction and good allylic atom abstractor! low inversion barrier for vinyl radical!1000x faster 2 C C 2 2 C C 2 2 C C 2 Br Br 75% Jasperse, C. P.; Curran, D. P.; Fevig, T. L. Chem. ev. 1991, 91, Stork, G.; Baine,.. J. Am. Chem. Soc 1982, 104,
21 ! Vinyl radical in the total synthesis of norseychellanone Br LDA Br Br Bu 3 Sn cat. AIB irradiation 70% 2, Pd/C 85:15!/" norseychellanone Stork, G.; Baine,.. Tetrahedron Lett. 1985, 26,
22 ! Activated olefins to aid 6-endo cyclization EWG on "electrophile" lowers LUM energy I Bu 3 Sn, AIB Ph, 85 C 97% 1. TMSI 2. Bu 3 Sn, AIB 45% alliacolide Ladlow, M.; Pattenden, G. Tetrahedron Lett. 1985, 26,
23 ! Activated olefins to aid 6-endo cyclization EWG on "electrophile" lowers LUM energy I Bu 3 Sn, AIB Ph, 85 C 97% 1. TMSI 2. Bu 3 Sn, AIB 45% mcpba alliacolide Ladlow, M.; Pattenden, G. Tetrahedron Lett. 1985, 26,
24 ! Enones as radical acceptor activators! Empirical evidence! Frontier orbital theory explanation C C 2500x faster SM LUM M Giese, B. Angew. Chem. Int. Ed. Engl. 1983, 22,
25 ! The triquinane system hirsutene! 9(12) -capnellene Curran, D.P.; akiewicz, D.M. J. Am. Chem. Soc. 1985, 107, Curran, D.P.; Chen, M.-. Tetrahedron Lett. 1985, 26, 4991.
26 ! The triquinane system hirsutene! 9(12) -capnellene Curran, D.P.; akiewicz, D.M. J. Am. Chem. Soc. 1985, 107, Curran, D.P.; Chen, M.-. Tetrahedron Lett. 1985, 26, 4991.
27 I Bu 3 Sn, AIB (cat.) Ph (0.02 M), reflux, 80% 5-exo-trig Bu 3 Sn 5-exo-dig hirsutene Curran, D.P.; akiewicz, D.M. J. Am. Chem. Soc. 1985, 107, 1448.
28 I Bu 3 Sn, AIB (cat.) Ph (0.02 M), reflux, 80% 5-exo-trig Bu 3 Sn 5-exo-dig hirsutene Curran, D.P.; akiewicz, D.M. J. Am. Chem. Soc. 1985, 107, 1448.
29 ! 1, 2, and 3 alkyl radicals have similar reactivities 80% hirsutene 80%! 9(12) -capnellene Curran, D.P.; akiewicz, D.M. J. Am. Chem. Soc. 1985, 107, Curran, D.P.; Chen, M.-. Tetrahedron Lett. 1985, 26, 4991.
30 ! A common natural product for radical cyclization strategies C 2 (+)-Prostaglandin F 2!
31 ! Stork's tandem vicinal difunctionalization strategy Et I Bu 3 SnCl (0.1 eq.) acb 3 (2.0 eq.) h!, TF, T Et Et Si 3 TBS C 5 11 TBS TBS Giese reaction Et Et Et C " 2. Pd(Ac)2 58% Si 3 C 5 11 in situ Bu 3 Sn Si 3 C 5 11 TBS TBS TBS Stork, G.; Sher, P. M.; Chen,.-L. J. Am. Chem. Soc. 1986, 108,
32 ! Keck's attempt at PGF 2! Et I Bu 3 Sn C 5 11 Et - Bu 3 Sn Et Ph, reflux C % C 5 11 TBS C C TBS SnBu 3 TBS Keck, G. E.; Burnett, D. A. J. rg. Chem. 1987, 52, 2958.
33 ! The fragmentation method! Keck applies allylation to perhydrohistrionicotoxin synthesis Br 2 h! SnBu 3 SnBu 3 - Bu 3 Sn Bu perhydrohistrionicotoxin Keck, G. E.; Yates, J. B. J. rg. Chem. 1982, 47, 3590.
34 ! Intramolecular Keck allylation SePh 1. Bu 3 SnLi 2. Ac 2 SePh Ac SnBu 3 Bu 3 Sn 88% directed introduction of unsaturation Ac 3-demethoxyerythratidinone Danishefsky, S. J.; Panek, J. S. J. Am. Chem. Soc. 1987, 109, 917.
35 ! Keck allylation for use in scholarisine A C- arylation I scholarisine A C 2 tandem vicinal difunctionalization C 2 X Smith, M. W.; Snyder, S. A. J. Am. Chem. Soc. 2013, 135,
36 ! Keck allylation for use in scholarisine A C- arylation I scholarisine A C 2 tandem vicinal difunctionalization C 2 X Smith, M. W.; Snyder, S. A. J. Am. Chem. Soc. 2013, 135,
37 ! Keck allylation for use in scholarisine A C 2 SnBu 3 Boc Br Et 3 B, Ph, 75 C, air 59% C 2 (3 steps) C 2 C 2 SnBu 3 C 2 Boc Boc Boc Smith, M. W.; Snyder, S. A. J. Am. Chem. Soc. 2013, 135,
38 ! Keck allylation for use in scholarisine A C 2 SnBu 3 Boc Br Et 3 B, Ph, 75 C, air 59% C 2 (3 steps) C 2 C 2 SnBu 3 C 2 Boc Boc Boc Smith, M. W.; Snyder, S. A. J. Am. Chem. Soc. 2013, 135,
39 ! Keck allylation for use in scholarisine A I Bu 3 Sn, AC, Ph,! [] scholarisine A Smith, M. W.; Snyder, S. A. J. Am. Chem. Soc. 2013, 135,
40 ! Keck allylation for use in scholarisine A I Bu 3 Sn, AC, Ph,! [] scholarisine A Smith, M. W.; Snyder, S. A. J. Am. Chem. Soc. 2013, 135,
41 ! Keck allylation for use in scholarisine A I Bu 3 Sn, AC, Ph,! [] scholarisine A Smith, M. W.; Snyder, S. A. J. Am. Chem. Soc. 2013, 135,
42 ! Keck allylation for use in scholarisine A I Bu 3 Sn, AC, Ph,! [] scholarisine A Smith, M. W.; Snyder, S. A. J. Am. Chem. Soc. 2013, 135,
43 ! Keck allylation for use in scholarisine A I Bu 3 Sn, AC, Ph,! [] scholarisine A Smith, M. W.; Snyder, S. A. J. Am. Chem. Soc. 2013, 135,
44 ! Keck allylation for use in scholarisine A I Bu 3 Sn, AC, Ph,! [] scholarisine A Smith, M. W.; Snyder, S. A. J. Am. Chem. Soc. 2013, 135,
45 ! Aryl radicals utilized as hydrogen atom abstractors 18% I Bu 3 Sn, AC, Ph,! 6% Smith, M. W.; Snyder, S. A. J. Am. Chem. Soc. 2013, 135,
46 ! Parker and Fokas: (-)-morphine via radical cyclization and fragmentation SPh Ts Ts Br Ts nbu 3 Sn, AIB Ph, reflux SPh 5-exo-trig SPh geometric constraints prevent 5-exo 6-endo-trig - PhS 30% SPh Ts fragmentation Ts (-)-morphine Parker, K. A.; Fokas, D. J. Am. Chem. Soc. 1992, 114,
47 ! Parker and Fokas: (-)-morphine via radical cyclization and fragmentation SPh Ts Ts Br Ts nbu 3 Sn, AIB Ph, reflux SPh 5-exo-trig SPh geometric constraints prevent 5-exo 6-endo-trig - PhS 30% SPh Ts fragmentation Ts (-)-morphine Parker, K. A.; Fokas, D. J. Am. Chem. Soc. 1992, 114,
48 ! Parker and Fokas: (-)-morphine via radical cyclization and fragmentation SPh Ts Ts Br Ts nbu 3 Sn, AIB Ph, reflux SPh 5-exo-trig SPh geometric constraints prevent 5-exo 6-endo-trig - PhS 30% SPh Ts fragmentation Ts (-)-morphine Parker, K. A.; Fokas, D. J. Am. Chem. Soc. 1992, 114,
49 ! Parker and Fokas: (-)-morphine via radical cyclization and fragmentation SPh Ts Ts Br Ts nbu 3 Sn, AIB Ph, reflux SPh 5-exo-trig SPh geometric constraints prevent 5-exo 6-endo-trig - PhS 30% SPh Ts fragmentation Ts (-)-morphine Parker, K. A.; Fokas, D. J. Am. Chem. Soc. 1992, 114,
50 ! Parker and Fokas: (-)-morphine via radical cyclization and fragmentation SPh Ts Ts Br Ts nbu 3 Sn, AIB Ph, reflux SPh 5-exo-trig SPh geometric constraints prevent 5-exo 6-endo-trig - PhS 30% SPh Ts fragmentation Ts (-)-morphine Parker, K. A.; Fokas, D. J. Am. Chem. Soc. 1992, 114,
51 ! Titanium(III)-induced cyclization of epoxyolefins 2Cp 2 TiCl 2 C C 2 68% 2 C C 2 85:15 cis:trans 3 + Cp 2 (Cl)Ti Cp 2 (Cl)Ti Cp 2 (Cl)Ti Ti(Cl)Cp 2 2 C C 2 2 C C 2 2 C C 2 ugent, W. A.; ajanbabu, T. V. J. Am. Chem. Soc. 1988, 110,
52 ! Titanium(III)-induced cyclization of epoxyolefins 2Cp 2 TiCl 2 C C 2 68% 2 C C 2 85:15 cis:trans 3 + Cp 2 (Cl)Ti Cp 2 (Cl)Ti Cp 2 (Cl)Ti Ti(Cl)Cp 2 2 C C 2 2 C C 2 2 C C 2 ugent, W. A.; ajanbabu, T. V. J. Am. Chem. Soc. 1988, 110,
53 ! Epoxides as!-alkoxy radical cyclization precursors 2 Entecavir Antiviral agent against epatitis B BMS patent to expire in 2015 in U.S. TBS Ac 20 mol% Cp 2 TiCl 2, 10 mol% IrCl(C)(PPh 3 ) 2 TBS Mn (2 eq.), collidine, TMSCl, 2 (4 bar), TF, 4 hr. T 58% Ac Velasco, J. et. al. J. rg. Chem. 2013, 78,
54 ! Epoxides as!-alkoxy radical cyclization precursors 1/2 M 1/2 MCl 2 Ac TBS Cp 2 TiCl 2 Cp 2 TiCl TBS Ac IrCl(C)(PPh 3 ) 2, 2, collidine, TMSCl L n Ti III Ac Ti III L n L n Ti III TBS TBS Ac L n Ti III TBS Ac Velasco, J. et. al. J. rg. Chem. 2013, 78,
55 ! The reductive method -X e - + X - ' ' e - anionic chemistry ' + ' Jasperse, C. P.; Curran, D. P.; Fevig, T. L. Chem. ev. 1991, 91,
56 ! The reductive method more commonly used to generate ketyl radicals SmI 2 ' ' =, alkyl e - anionic chemistry ' + ' Jasperse, C. P.; Curran, D. P.; Fevig, T. L. Chem. ev. 1991, 91,
57 ! The triquinane system using SmI 2 hypnophilin Fevig, T. L.; Elliott,. L.; Curran, D. P. J. Am. Chem. Soc. 1988, 110,
58 ! The triquinane system using SmI 2 SmI 2 SmI 2, TF/DMPU 69% SmI SmI 2 2 Fevig, T. L.; Elliott,. L.; Curran, D. P. J. Am. Chem. Soc. 1988, 110,
59 ! Kilburn's stereoselective synthesis of paeonilactone B via a SmI 2 cyclization SmI 2, MPA, tbu TF, 0 to T 63% Sm III L n Sm III L n Sm III L n 10:1 diastereomers MPA thought to cooridnate to Sm III to add bulk and induce stereoselectivity Boffey,. J.; Wittingham, W. G.; Kilburn, J. D. J. Chem. Soc., Perkin Trans. 1, 2001,
60 ! SmI 2 for macrocyclizations in Diazonamide A Cbz SmI 2, DMA 40-45% Cbz 2 Bn MM Bn MM Cl Cl diazonamide A icolaou, K. C. et. al. ACIEE 2003, 42, 1753.
61 ! SmI 2 for macrocyclizations in Diazonamide A Cbz SmI 2, DMA 40-45% Cbz 2 Bn MM Bn MM Cbz SmI 2 I 2 Sm Bn MM icolaou, K. C. et. al. ACIEE 2003, 42, 1753.
62 ! adical cyclizations in sugar chemistry Bn SePh Bu 3 Sn, AIB, 90% Bn Bn Bn Bn Bn Bn S 2 Ph SmI 2, MPA, 78% Bn Bn Bn Bn Bn Bn SePh Et 3 B, Bu 3 Sn, T, 72% Bn Bn Bn Bn Bn De smaeker, A. et. al. Tetrahedron Lett. 1989, 30, Sinay, P. et. al. Tetrahedron Lett. 1992, 33, Czernecki, S.; Ayadi, E.; Xie, J. Tetrahedron Lett. 1996, 37,
63 ! Tethered alkene and alkyne radical acceptors Ph Si SePh Ph 1. Bu 3 Sn, AIB 2. TBAF 73% E:Z >20:1 Bn SePh Bu 3 Sn, AIB Bn Bn TBDMS Bn Bn 89% Bn Bn Bn Bn De smaeker, A. et. al. Tetrahedron Lett. 1989, 30, Stork, G.; Suh,. S.; Kim G. J. Am. Chem. Soc. 1991, 113,
64 ! 9-endo cyclization for!"c-disaccharides Bn Bn Bn Si SePh Bn Bn 1. Bu 3 Sn, AIB 2. F, TF 40% Bn Bn Bn Bn Bn 6, 2' adduct! 8-endo cyclization for #"C-disaccharides Bn Bn Bn SePh Si Bn Bn 1. Bu 3 Sn, AIB 2. TBAF 45% Bn Bn Bn Bn Bn 3, 2' adduct Xin, Y. C.; Mallet, J.-M.; Sinay, P. J. Chem. Soc., Chem. Commun. 1993,
65 ! 5-exo SmI 2 cyclization for C-disaccharides Bn Bn Bn S 2 Pyr Si Bn Bn Bn 1. SmI 2, TF 2. TBAF, TF 3. Pd/C, 2 4. Ac 2, Py 48% Bn Bn Bn Ac Ac Ac Ac! no MPA makes SmI 2 weaker reductant! LUM!* of S 2 Ar lowered with 2-pyridine! less toxic conditions Mazeas, D.; Skrydstrup, T.; Doumeix,.; Beau, J.-M. Angew. Chem. Int. Ed. Engl. 1994, 33,
66 Bn t-bu 2 CC PPh 3 t-bu 2 C Bn Bn Bn Bn DCM, 92% Bn commercially available 2:3 E:Z 1. 2 S, (CCl) 2, Et 3, 96% 2. TFA, DCM, 0 C, 93% 2 C Bn Br 2 C Bn Bn 1. LDA 2. C 2 Br 2 3. LDA, C % 2 C Bn Bn Bn 5 equiv. Bu 3 Sn, Ph, T 85% 2 C Bn Bn BrC Bn 2 C Bn Bn Bn carba-d-fructo-furanose Wilcox, C. S.; Gaudino, J. J. J. Am. Chem. Soc. 1986, 108,
67 Bn t-bu 2 CC PPh 3 t-bu 2 C Bn Bn Bn Bn DCM, 92% Bn commercially available 2:3 E:Z 1. 2 S, (CCl) 2, Et 3, 96% 2. TFA, DCM, 0 C, 93% 2 C Bn Br 2 C Bn Bn 1. LDA 2. C 2 Br 2 3. LDA, C % 2 C Bn Bn Bn 5 equiv. Bu 3 Sn, Ph, T 85% 2 C Bn Bn BrC Bn 2 C Bn Bn Bn carba-d-fructo-furanose Wilcox, C. S.; Gaudino, J. J. J. Am. Chem. Soc. 1986, 108,
68 Bn t-bu 2 CC PPh 3 t-bu 2 C Bn Bn Bn Bn DCM, 92% Bn commercially available 2:3 E:Z 1. 2 S, (CCl) 2, Et 3, 96% 2. TFA, DCM, 0 C, 93% 2 C Bn Br 2 C Bn Bn 1. LDA 2. C 2 Br 2 3. LDA, C % 2 C Bn Bn Bn 5 equiv. Bu 3 Sn, Ph, T 85% 2 C Bn Bn BrC Bn 2 C Bn Bn Bn carba-d-fructo-furanose Wilcox, C. S.; Gaudino, J. J. J. Am. Chem. Soc. 1986, 108,
69 Bn t-bu 2 CC PPh 3 t-bu 2 C Bn Bn Bn Bn DCM, 92% Bn commercially available 2:3 E:Z 1. 2 S, (CCl) 2, Et 3, 96% 2. TFA, DCM, 0 C, 93% 2 C Bn Br 2 C Bn Bn 1. LDA 2. C 2 Br 2 3. LDA, C % 2 C Bn Bn Bn 5 equiv. Bu 3 Sn, Ph, T 85% 2 C Bn Bn BrC Bn 2 C Bn Bn Bn carba-d-fructo-furanose Wilcox, C. S.; Gaudino, J. J. J. Am. Chem. Soc. 1986, 108,
70 Bn t-bu 2 CC PPh 3 t-bu 2 C Bn Bn Bn Bn DCM, 92% Bn commercially available 2:3 E:Z 1. 2 S, (CCl) 2, Et 3, 96% 2. TFA, DCM, 0 C, 93% 2 C Bn Br 2 C Bn Bn 1. LDA 2. C 2 Br 2 3. LDA, C % 2 C Bn Bn Bn 5 equiv. Bu 3 Sn, Ph, T 85% 2 C Bn Bn BrC Bn 2 C Bn Bn Bn carba-d-fructo-furanose Wilcox, C. S.; Gaudino, J. J. J. Am. Chem. Soc. 1986, 108,
71 Bn t-bu 2 CC PPh 3 t-bu 2 C Bn Bn Bn Bn DCM, 92% Bn commercially available 2:3 E:Z 1. 2 S, (CCl) 2, Et 3, 96% 2. TFA, DCM, 0 C, 93% 2 C Bn Br 2 C Bn Bn 1. LDA 2. C 2 Br 2 3. LDA, C % 2 C Bn Bn Bn 5 equiv. Bu 3 Sn, Ph, T 85% 2 C Bn Bn BrC Bn 2 C Bn Bn Bn carba-d-fructo-furanose Wilcox, C. S.; Gaudino, J. J. J. Am. Chem. Soc. 1986, 108,
72 Bn t-bu 2 CC PPh 3 t-bu 2 C Bn Bn Bn Bn DCM, 92% Bn commercially available 2:3 E:Z 1. 2 S, (CCl) 2, Et 3, 96% 2. TFA, DCM, 0 C, 93% 2 C Bn Br 2 C Bn Bn 1. LDA 2. C 2 Br 2 3. LDA, C % 2 C Bn Bn Bn 5 equiv. Bu 3 Sn, Ph, T 85% 2 C Bn Bn BrC Bn 2 C Bn Bn Bn carba-d-fructo-furanose Wilcox, C. S.; Gaudino, J. J. J. Am. Chem. Soc. 1986, 108,
73 ! The oxidative method! Chemical oxidation ' ' M +n - + ' + M +n-1 ' " " M +n " product ' '! Electrochemical oxidation Kolbe electrolysis -e - -C 2 2 -C [ -C 2 ] 2 - Jasperse, C. P.; Curran, D. P.; Fevig, T. L. Chem. ev. 1991, 91,
74 ! The oxidative method! Chemical oxidation ' ' M +n - + ' + M +n-1 ' " " M +n " product ' '! Electrochemical oxidation Kolbe electrolysis -e - -C 2 2 -C [ -C 2 ] 2 - Jasperse, C. P.; Curran, D. P.; Fevig, T. L. Chem. ev. 1991, 91,
75 ! The oxidative method! Chemical oxidation ' ' M +n - + ' + M +n-1 ' " " M +n " product ' '! Electrochemical oxidation Kolbe electrolysis -e - -C 2 2 -C [ -C 2 ] 2 - Jasperse, C. P.; Curran, D. P.; Fevig, T. L. Chem. ev. 1991, 91,
76 ! xidative quadruple cyclization to prepare tetracyclic diterpenes C 2 Et Mn(Ac) 3, Cu(Ac) 2, T, 3 h 35% C 2 Et C 2 Et isosteviol beyer-15-ene-3,9-diol Snider, B.B.; Kiselgof, J. Y.; Foxman, B. M. J. rg. Chem. 1990, 112,
77 ! xidative quadruple cyclization by Snider C 2 Et C 2 Et Mn(III) Mn(Ac) 3, Cu(Ac) 2, T, 3 h 35% * C 2 Et C 2 Et Cu(II) only other epimer isolated C 2 Et C 2 Et C 2 Et Snider, B.B.; Kiselgof, J. Y.; Foxman, B. M. J. rg. Chem. 1990, 112,
78 ! xidative quadruple cyclization by Snider C 2 Et C 2 Et Mn(III) Mn(Ac) 3, Cu(Ac) 2, T, 3 h 35% * C 2 Et C 2 Et Cu(II) only other epimer isolated C 2 Et C 2 Et C 2 Et Snider, B.B.; Kiselgof, J. Y.; Foxman, B. M. J. rg. Chem. 1990, 112,
79 ! xidative quadruple cyclization by Snider C 2 Et C 2 Et Mn(III) Mn(Ac) 3, Cu(Ac) 2, T, 3 h 35% * C 2 Et C 2 Et Cu(II) only other epimer isolated C 2 Et C 2 Et C 2 Et Snider, B.B.; Kiselgof, J. Y.; Foxman, B. M. J. rg. Chem. 1990, 112,
80 ! xidative quadruple cyclization by Snider C 2 Et C 2 Et Mn(III) Mn(Ac) 3, Cu(Ac) 2, T, 3 h 35% * C 2 Et C 2 Et Cu(II) only other epimer isolated C 2 Et C 2 Et C 2 Et Snider, B.B.; Kiselgof, J. Y.; Foxman, B. M. J. rg. Chem. 1990, 112,
81 ! xidative quadruple cyclization by Snider C 2 Et C 2 Et Mn(III) Mn(Ac) 3, Cu(Ac) 2, T, 3 h 35% * C 2 Et C 2 Et Cu(II) only other epimer isolated C 2 Et C 2 Et C 2 Et Snider, B.B.; Kiselgof, J. Y.; Foxman, B. M. J. rg. Chem. 1990, 112,
82 ! xidative quadruple cyclization by Snider C 2 Et C 2 Et Mn(III) Mn(Ac) 3, Cu(Ac) 2, T, 3 h 35% * C 2 Et C 2 Et Cu(II) only other epimer isolated C 2 Et C 2 Et C 2 Et Snider, B.B.; Kiselgof, J. Y.; Foxman, B. M. J. rg. Chem. 1990, 112,
83 Ph garcibracteatone Mn(Ac) 3, Cu(Ac) 2, Ac, T, 3 hrs Pepper,. P.; Lam,. C.; Bloch, W. M.; George, J.. rg. Lett. 2012, 14,
84 ! The oxidative method Ph Mn(Ac) 3, Cu(Ac) 2, Ac, T, 3 hrs garcibracteatone 14% 5-epi-garcibracteatone 8%! 4 C-C bonds formed! no protecting groups! 5 stereocenters formed! biomimetic pathway Pepper,. P.; Lam,. C.; Bloch, W. M.; George, J.. rg. Lett. 2012, 14,
85 Ph garcibracteatone Mn(Ac) 3, Cu(Ac) 2, Ac, T, 3 hrs Pepper,. P.; Lam,. C.; Bloch, W. M.; George, J.. rg. Lett. 2012, 14,
86 Ph garcibracteatone Mn(Ac) 3, Cu(Ac) 2, Ac, T, 3 hrs Pepper,. P.; Lam,. C.; Bloch, W. M.; George, J.. rg. Lett. 2012, 14,
87 Ph garcibracteatone Mn(Ac) 3, Cu(Ac) 2, Ac, T, 3 hrs Pepper,. P.; Lam,. C.; Bloch, W. M.; George, J.. rg. Lett. 2012, 14,
88 Ph garcibracteatone Mn(Ac) 3, Cu(Ac) 2, Ac, T, 3 hrs Pepper,. P.; Lam,. C.; Bloch, W. M.; George, J.. rg. Lett. 2012, 14,
89 ! So what is "radical" now?! Total syntheses with radical cyclizations method in the last year: Tin eagent: 8 reported eduction: 6 reported xidation: 6 reported! o photoredox radical cyclization in total synthesis yet! adical cyclization still primarily for carbon-carbon bond formations! Many use fragmentation method - for functional handle after! Total syntheses with tandem radical cyclization in the last year: Tandem: 5
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