Kurs: Metallorganische Reagenzien. Cericammoniumnitrate (CAN)

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1 Kurs: Metallorganische eagenzien Cericammoniumnitrate (CAN) by Laura Munoz Senovilla and Arthur Fedoseev.

2 CAN as one-electronelectron oxidant

3 CAN as one-electron electron oxidant Based on: Salt of high-valent metal Solubility in organic solvents Methanol Acetonitrile il Low toxicity Ease of handling Eº = 1.6 ev

4 CAN as one-electron oxidant C-C Bond Formation C- Heteroatom Bond Formation

5 CAN as one-electron oxidant C-C Bond Formation C- Heteroatom Bond Formation

6 C-C C Bond Formation CAN-mediated Intermolecular eactions: xidative Addition to Alkenes and Dienes: verall yields Mild reaction conditions Experimental simplicity CAN-mediated d Intramolecular l eactions: xidative Intramolecular Annulation: Low yields Little use

7 C-C Bond Formation Intermolecular eactions xidative Addition to Alkenes:

8 C-C Bond Formation Intermolecular eactions xidative Addition to Alkenes: + Ph Ph I II Ph Ph III

9 C-C Bond Formation Intermolecular eactions xidative Addition to Dienes:

10 C-C C Bond Formation CAN-mediated Intermolecular eactions: xidative Addition to Alkenes and Dienes: CAN-mediated Intramolecular eactions: xidative Intramolecular Annulation: Low yields Little use

11 C-C Bond Formation Intramolecular eactions xidative Intramolecular eactions:

12 CAN as one-electron oxidant C-C Bond Formation C- Heteroatom Bond Formation

13 Cer(IV)ammoniumnitrate (CAN) CAN als ein Elektron xidationsmittel. Kohlenstoff- Heteroatombindungsknüpfung 2 N N 2 2- Ce N 2 ecycling von CAN durch Elektrolyse. 2 N N 2 N 2 2 (NH 4 ) 2 2+

14 Cer(IV)ammoniumnitrate (CAN)

15 Cer(IV)ammoniumnitrate (CAN) NaN 3, CAN, 2 N 3 in MeCN, 0 C 14-50% X NaN 3, CAN, argon N 3 in MeH, 0 C 14-50% % N 3 X = Me, N 2

16 Cer(IV)ammoniumnitrate (CAN) NaNN 3, CAN, 2 N 3 in MeH, 0 C 14-50%

17 Cer(IV)ammoniumnitrate (CAN) N 3 2 N Ce N 3 N 2 X NaN 3, CAN, argon N 3 in MeH, 0 C 14-22% X = Me, N 2

18 Cer(IV)ammoniumnitrate (CAN) I NaN 3,NaI,CAN N 3 in MeH, T = H (71%) N 2 Me (70%) Cl (78%) N 2 (66%) S 2 Ar ArS 2 Na, CAN MeCN, T, 45 min. (61%) S 2 Ar (20%)

19 Cer(IV)ammoniumnitrate (CAN) SCN NH 4 SCN, CAN SCN MeCN, T 65-95%

20 Cer(IV)ammoniumnitrate (CAN): ingöffnungsreaktionen. H N 3 Ph NaN 3, CAN, t-buh reflux Ph N 3 65%(98:2) H Ph

21 Cer(IV)ammoniumnitrate (CAN): Insertion/Addition von Halogen KBr, CAN, CH 2 Cl 2 Br Ph H 2, T Ph Br Br Br KBr, CAN, CH 2 Cl 2 H 2, T (E:Z wie 2:3)

22 Cer(IV)ammoniumnitrate (CAN): Addition von Brom an Dobi. HN CAN, LiBr HN Br N N = Me, H CAN + MX 1/2 X 2 + Ce(III) 1/2 X + "X + 2 CAN "+Ce(III)

23 ecycling von (CAN) durch Elektrolyse

24 CAN as Protection and Deprotection Catalyst

25 CAN as Protection ti and Deprotection ti Catalyst t Protection Catalyst : Carbonyl Compounds as 1,3-xathianes Deprotection Catalyst: Hydroxyl Compounds as THP and THF Chemoselective Deprotection of Ketals and THP Ethers in the presence of Enol Triflates ß-keto Enol Ethers

26 CAN as Protection Catalyst Carbonyl Compounds as 1,3-xathianes: Properties: General stability under both acidic and basic conditions Versatile synthetic reagent for C-C Bond formation But: Limitations of using stoichiometric reagents Harsh reaction conditions Cumbersome reaction procedure

27 CAN as Protection Catalyst Carbonyl Compounds as 1,3-xathianes: 2-mercaptoethanol (exc); MeCN; CAN; 10h; T

28 CAN as Deprotection Catalyst Hydroxyl Compounds as THP and THF: Properties: Powerful and highly selective Lewis acid High yields (80%- 100%) emarkable selectivities toward several protecting groups Chemoselective unmasking

29 CAN as Deprotection Catalyst Hydroxyl Compounds as THP and THF: THP H S THP S H S S THF H

30 CAN as Deprotection Catalyst Hydroxyl Compounds as THP and THF: emarkable selectivity: + S THP tbu S tbu : 0 H

31 CAN as Deprotection Catalyst Chemoselective Deprotection ti of Ketals and THP Ether: In the Presence of Enol Triflates: eaction conditions: Quantitative Ketals and THP Ether yields (>95%) No hydrolysis of the Enol Triflates

32 Chemoselective Deprotection of Ketals and THP Ether

33 Chemoselective Deprotection of Bifunctional Substrates Tf Tf Tf Tf TBDMS H

34 CAN as Deprotection Catalyst Synthesis of ß-keto Enol Ethers from Cyclic ß-Diketones and their deprotection: CAN (10mol%) 1 H or 2 H, rt, 7-35min H CAN (10 mol %) H 2 -CH 3 CN (1:1) reflux, 0.5-3h 1 = H or CH 3

35 Literatur Tetrahedron Letters 50 (2009) (Ceric ammonium nitrate (CAN) as oxidizing or nitrating reagent for organic reactions in ionic liquids.) Asakura, J.; obins, M. J. J. rg. Chem. 1990, 55, Accounts of Chemical esearch, Vol.37, No.1, 2004 (ecent Advances in Synthetic Transformations Mediated by Cerium (IV) Ammonium Nitrate Synthetic Communications, Vol.32, No15, pp , 2002 (Ceric Ammonium Nitrate as a Convincent catalys for Protection of Carbonyl Compounds as 1,3- xathianes Tetrahedron Letters 40 (1999) (emarkable Deprotection of THP and THF Ethers Catalysed by Cerium Ammonium Nitrate (CAN) Under Neutral Conditions Chemistry Letters Vol.35, No. I 2006 (Cerium (IV) Ammonium Nitrate-catalyzed Synthesis of β Keto Enol Ethers from Cyclic β Diketones and Their deprotection) Thieme e Journals, 2005 (Cerium (IV) Ammonium Nitrate Catalysed Hoghly Chemoselective Deprotection of Ketals and THP Ethers in the presence of Enol Triflates)