Baeyer-Villiger Oxidation

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A micro-review of the Baeyer-Villiger oxidation with recent (2012/2013) references from the literature; last updated on March 1 2013.

The Baeyer-Villiger Oxidation is a popular tool for the synthesis of esters and lactones.

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Baeyer-Villiger Oxidation

  1. 1. Baeyer-Villiger Oxidation The Baeyer-Villiger oxidation, also known as the Baeyer-Villiger rearrangement, was first reported on December 17, 1899 by Adolf Baeyer and Victor Villiger in Chemische Berichte. It is a popular synthetic tool for the conversion of acyclic ketones to esters and cyclic ketones to lactones, of which the latter are precursors to hydroxy acids and acyclic diols. Aromatic aldehydes bearing alkoxy substituents can be converted to the corresponding fomates and phenols. The original contribution of Baeyer and Villiger referred to the conversion of the cyclic ketones menthone (1) and tetrahydrocarvone (2) to the respective lactones by monoperoxysulfuric acid, also known as Caro’s acid: O O O O O O H2SO5 H2SO5 (1) (2) Since then, the utility, regioselectivity and stereospecificity of the reaction has been extended by new transition metal catalysts, zeolite based catalysts, alumina, mesoporous catalysts, enzymes and the application of ultrasound. Metachloroperoxybenzoic acid (MCPBA), peroxybenzoic acid (PBA), and trifluoroperoxyacetic acid (TFPAA) are among the most common peracids used. More recent reagent systems include the magnesium salt of monoperoxyphthalic acid (MMPP), sodium perborate,sodium percarbonate, hydrogen peroxide in the presence of boron trifluoride or diselenides. Catalytic Baeyer-Villiger oxidations were feasible with methyltrioxorhenium and hydrogen peroxide in the ionic liquid [bmim]BF4 . Oxone has been used to effect the oxidation in [bmim]BF4. Potassium peroxomonosulfate supported on hydrated silica (‘reincarnated Caro’s acid’) is also known; the reaction is more efficient when carried out in supercritical carbon dioxide. Molecular oxygen has been used to effect a variety of Baeyer-Villiger oxidations at room temperature. Recently introduced catalysts include pentafluorophenyl borates, mesoporous zirconium phosphate and graphite. Baeyer-Villiger monooxygenases have found increasing application through the development of recombinant bacteria and fungi. The monoxygenases depend on flavin (FAD) as a cofactor and a molecule such as NADPH or NADH to act as a reducing agent. Advantages associated with the application of monoxygenases include high regioselectivity and enantioselectivity. MCPBA preferentially yields the corresponding epoxide in the presence of a double bond, at low temperature in an inert solvent without the presence of an acid catalyst. Application of bis[trimethylsilyl] peroxide (BTSP) minimizes epoxide formation when an alkene is present. It was demonstrated that BTSP can also be used as an effective reagent in the ionic liquid 1-n-butyl-3-methylimidazolium trifluoromethanesulfonate (bmimOTf). See page 14. Base catalyzed rearrangements are less common. The mechanistically similar Dakin reaction is generally conducted in basic conditions, leading to phenols and catechols from aromatic aldehydes. See page 4 and compare with example 12 in page 7. 1
  2. 2. Mechanism The most accepted mechanism is that proposed by Criegee, or a variation of it. Salient features of the mechanism are. 1) Retention of stereochemistry by the migrating group. 2) Migration is concerted with the departure of the leaving group. The concerted step is rate determining. 3) Migrating groups with greater electron donating power have correspondingly greater migratory aptitude because of the increased ability to stabilize a positive charge in the transition state. This renders stereoselectivity to the oxidation of unsymmetrical ketones. The general order of migration is: tertiary alkyl > cyclohexyl > secondary alkyl > benzyl > phenyl > primary alkyl > H 4) Migration is favored when the migrating (Rm ) group is antiperiplanar to the O-O bond of the leaving group; this is known as the primary stereoelectronic effect. The antiperiplanar alignment of the lone pair of electrons on oxygen with the migrating group is the secondary stereoelectronic effect. O O Rm O COR' R H primary secondary 4) Electron withdrawing groups on the peroxyacid and peroxide enhance the rate of rearrangement. The mechanism can be depicted as in Scheme (I): R R O H R R O H O O R OH R R O H O O O R H R OR O H R OR O R R O H O O O R H Scheme I Baeyer-Villiger oxidation of cyclohexanone is represented in Scheme II. Schemes I and II provide general reaction mechanisms for acid catalyzed reactions. 2
  3. 3. O H O H O R O O H O H O O O R O O H O O H Scheme II Scheme III represents the rearrangement of the Criegee intermediate in a cyclical manner. Rm R O O H O O R' Scheme III In the case of haloketones, migration tends to occur from the non-halogenated carbon. Reactions conducted in non-polar solvents may follow a non-ionic mechanism; see additional notes and references. Baeyer-Villiger reaction of benzaldehydes often proceed by migration of the hydride ion instead of the aryl group. In a study by Adejare, hydride ion migration occurred faster than phenyl ion migration when the phenyl group had halogen substituents, resulting in the formation of carboxylic acid instead of phenol; aromatic aldehydes possessing electron withdrawing groups have a strong tendency to produce the corresponding carboxylic acids, in contrast to aromatic aldehyde(s) with electron donating group(s). Journal of Fluorine Chemistry (2000), 105, 107. F Br CHO F Br COOH CH2Cl2, reflux (74%) MCPBA 3
  4. 4. A recent and interesting development is the selective transformation of both primary aliphatic aldehydes and aromatic aldehydes to formates involving a hypervalent λ3 -bromane, by Ochiai. The following pathway was proposed by Ochiai. R O R' H2O R R' HO OH + Br CF3 F F R' R OH O Br F Ar ArBr R' O OR Br (III) Criegee intermediate Journal of the American Chemical Society (2010), 32, 9236. See page 12 for corresponding examples. The Dakin reaction is portrayed here for comparison. HO O R H O O HO R O O O H O HO O R OH HO H2O, OH Recent examples of the Dakin reaction involving nucleophilic flavin catalysts are provided by the publications of Chen and Foss in Organic Letters (2012), 14,11, 2806-2809. An organometallic reaction proceeding through a mechanism similar to that of the Baeyer-Villiger rearrangement was demonstrated by Periana, where an aryltrioxorhenium species was oxidized to the corresponding phenol. Organometallics (2011),30, 2079. Re O O O YO YO = IO4, H2O2, PhIO4 Re O O OH O Y δ δ Examples follow; see pages 5-13. 4
  5. 5. Examples: O C6H13 O O C6H13 MMPP, NaHCO3 (1) (2) O J. Org. Chem (1997), 62, 2633. 95% O O O2, PhCHO Fe2O3, 200 C Angew. Chem. Int. Ed (1998), 37, 1198. 92% MeOH (3) O Na2CO3, H2O2, Ac2O O O ))) 6h Chemical Abstracts (1996), 123, 316192j. 84% (4) Tet. Lett (1977), 31, 2713. 69% MCPBA O O O (5) Cl O Cunninghamella echinulata Cl OH O Tet. Lett (1997), 38,1195. > 99% ee 31% (6) O CPMO O O CPMO = cyclopentanone monooxygenase Chem. Commun (1996), 2333. 98% ee quantitative 5
  6. 6. O Me O O Me CHMO =cyclohexanone monooxygenase J. Org. Chem (2003), 68, 6222. 99% ee 100% conversion (7) CHMO (8) O *Engineered e.coli cells O O * E. coli cells that overexpress cyclohexanone monooxygenase J. Org. Chem (2001), 66, 733. 48% (9) O H2O2 (60%) 1 mol % catalyst CF3CH2OH O O J. Org. Chem (2001), 66, 2429 99% Se F3C F3C 2 = catalyst (10) N Cbz H H O H Cl N Cbz H H H Cl O O MCPBA NaHCO3 CH2Cl2, rt, 30 min J. Org. Chem (2002), 67, 3651. 85%, only product 6
  7. 7. (12) CHO OMe O OMe O OH OMe catalyst, H2O2 MeCN, 80 0 C, 7 h 87% total conversion Beta-7 zeolite = catalyst SnO2 content = 0 %; Si:Al ratio = 30 (mol/mol) Journal of Catalysis (2004), 221, 67. 1% 95% (11) O O OH2O2 (35%), 1 mol % catalyst CF3C6F11, (CH2)2Cl2 93% Sn[N(SOCF17)2]4 = catalyst 25 0 C, 2h Tet. Lett (2003), 44, 4977. (13) O n MCPBA CH2Cl2, rt, 4d O x O O y Macromolecules (2004), 37, 4484. 73% ketone/ester = x/y = 82/18 (14) O catalyst, H2O2 t-BuOH, 650 C, 5h 60% COOH catalyst = 0.6 mol% Se)2 Se)2 Syn. Comm (1999), 29, 2981. 7
  8. 8. (15) O Ph 5.2 eq. 30% H2O2 5 mol% catalyst OTf Se 2 catalyst = 5 mol % O O Ph Tet. Lett (2005), 46, 8665. 85% CH2Cl2, RT, 24 h (16) O O O hydr-Sio2.KHSO3 sc CO2 250 bar, 400 C 96% J. Org. Chem (2006), 71, 6432. (17) O O O PhCHO, O2 ))) 2h, CCl4 87.7% Chemical Eng. Journal (2006), 121, 63. (18) N Ts O OBn MCPBA, NaHCO3 O N O Ts OBn 73% Tet. Lett (2006), 47, 4865. CH2Cl2 8
  9. 9. O O O O O 00 C, CH2Cl2, 1h H H H COOMe COOMe (a) (b) TFPAA a: b = 4: 1 75% Steroids (2007), 72, 466. (20) Me O COOMeCbzHN H Me O COOMeCbzHN H Ph PhO TFPAA 00 C, CH2Cl2, > 5 h J. Org. Chem (2008), 73, 2633.. 75% (19) COOMe 9
  10. 10. (21) Ph O O Ph O CHCl3, 18h H2O2, catalyst (10 mol%) 99% ee = 88% R Angewandte. Chem. Int. Ed (2008), 47, 2840. catalyst: O X P O OH O X = pyren-1-yl X (22) O HO HO O OPenicillium lilacinum AM111 dehydroepiandrosterone (DHEA) 36 h (85%) Steroids (2008), 73, 441-1445. (23) O OMe OMeH OMe MCPBA, PTSA CH2Cl2, rt OMe OMeH OMe O O 75% Tet. Lett (2010), 51, 93.. 10
  11. 11. (24) O O O MCPBA, NaHCO3 CH2Cl2, 00 C, 30 min O O 60% 30% + Tet. Lett (2009), 50, 4519. (25) BnO O MCPBA CH2Cl2, rt, 32h BnO OCOCH3 quantitative Org. Lett (2010), 12, 508. (26) Me H H OH Me O Me O Me Me Me H H OH OAc Me O Me Me 1,2 DCE rt, then 80 0 C, 48h MCPBA (4 eq) 65% JACS (2010), 132, 23, 8219. 11
  12. 12. (27) aryl bromane (1.5 eq) 68% JACS (2010), 132, 23, 9236. CH3CH2CHO CH3CH2OCHO H2O, CH2Cl2, 0 0 C PhCHO PhOCHO 98% aryl bromane: Br F F CF3 O Me O O Me 93% + O O Me 1% (28) Tet. Lett (2011), 52, 23, 458. O O O MCPBA (1.2 eq) 10 mol% CAN CH2Cl2, 0 0 C to rt, 6h 75% 12
  13. 13. (29) Tet. Lett (2012), 68, 9061-9068. MCPBA, CHCl3O Cl C8H17 C8H17 O O Cl p-TsOH, r.t, 16 days + O Cl H H O H 77 : 23 (30) O MCPBA CH2Cl2, r.t, 2 days O O 70% Angewandte. Chem.Int. Ed (2012), 51, 2485-2488 (32) 98%% J. Org. Chem (2013), 78, 93-103. O O H O MMPP O O H O O (31) O O O catalyst (1 mol%) 30% H2O2 (1.1 eq) 77% Angewandte Chemie International Edition (2012), 51,36, 9093-9096. catalyst: LiB(C6F5)4.2.5Et2O DCE (0.05M), 70 0 C 13
  14. 14. Additional Notes and References  An example of reversed regioselectivity was reported by Mikami and Yamanaka: O O O CF3 TFPAA ( 2.0 eq ) F3C quantitative O O CF3 not observed rt, CH2Cl2, 16h TFA ( 7.0 eq ) Organic Letters (2003),5, 25, 4803 Grein and Crudden published a study of the Baeyer-Villiger reaction of haloketones in the Journal of Organic Chemistry (2006), 71, 861. The reaction mechanism is reviewed in detail.  A scholarly review of the Baeyer-Villiger oxidation is given by Krow in volume 43 of Organic Reactions (1993). Renz and Meunier provide an excellent complementary discussion of historical aspects in the European Journal of Organic Chemistry (1999), 737- 750.  Mora-Diez and coauthors have argued against an ionic mechanism for Baeyer-Villiger oxidations conducted in non polar solvents; an alternative mechanism is presented, favoring concerted deprotonation during the addition and migration steps. Organic and Biomolecular Chemistry (2009), 7, 3682.  Lactone synthesis was accomplished using methyltrioxorhenium/hydrogen peroxide in N N BF4 the ionic liquid 1-n-butyl-3-methylimidazolium tetrafluoroborate[bmim]BF4, as reported in Tetrahedron Letters (2003), 44, 8991. Baeyer-Villiger oxidation of ketones with bis(trimethylsilyl) peroxide in the presence of bmimOTf resulted in yields exceeding 70%, except for the oxidation of tetralone. Green Chemistry (2009), 11, 279. Chrobok’s group performed the oxidation with oxone (2KHSO5.KHSO4.K2SO4) in a variety of ionic liquids; bmimBF4 and HmimOAc offered maximum yields (95-96%). Tetrahedron (2010), 66, 6212. 14
  15. 15.  The magnitude of the preference for antiperiplanar migration over gauche migration is discussed by Radkiewicz-Poutsma in the Journal of Organic Chemistry (2004), 69, 7148.  Microwave accelerated Baeyer-Villiger synthesis of lactones was investigated by Ritter: Tetrahedron (2006), 62, 4709.  Yamabe and Yamazaki recently discussed the role played by hydrogen bonds in the rearrangement; their opinions are expressed in the Journal of Organic Chemistry (2007), 72, 3031.  Zeolite based catalysts and clay based catalysts for Baeyer-Villiger oxidation were reviewed by Ruiz and Jimenez-Sanchidrian in Tetrahedron (2008), 64, 2011.  The mechanism of cyclohexanone monooxygenase is outlined in The Organic Chemistry of Drug Action. Silverman, Richard B. (2002). Academic Press. ISBN 0-12-643731-9. Enantioselectivities of recently isolated Baeyer-Villiger monooxygenases toward alkyl substituted cyclohexanones are reviewed in Tetrahedron (2009), 65, 947 and Chemical Reviews (2011), 111, 7, 4165. The role of FAD (flavin adenine dinucleotide) in enzymically catalyzed Baeyer-Villiger reactions is discussed by Walsh and Wencewicz in a recent review of flavoenzymes. Natural Product Reports (2013), 30, 175-200.  Application of platinum (II) catalysts in conjunction with chelating diphosphines is reviewed by Giorgio Strukul and co-authors in Coordination Chemistry Reviews (2010), 254, 646-660.  Lei and coworkers published an account of the use of silica supported sulfate acid catalyst to effect the Baeyer-Villiger oxidation in excellent yields (86-100%). Catalysis Communications (2011), 12, 798.  In addition to the examples given above (4, 10, 18, 23-26, 28-30), other citations of the recent application of meta-chloroperoxybenzoic acid to implement the Baeyer-Villiger oxidation are listed below. Journal of Organic Chemistry (2011), 76, 1662. Journal of Organic Chemistry (2011), 76, 2315. Chemical Communications (2011), 47, 3745. Tetrahedron (2012), 68, 47, 9612-9615.  Baeyer-Villiger oxidation at room temperature using molecular oxygen and benzaldehyde over mesoporous zirconium phosphate was demonstrated by Sinhamapatra and Sinha. Yields varied from 75% to 100% for the oxidation of alicyclic ketones. Similar yields were reported when MCPBA was substituted for molecular oxygen. Catalysis Science and Technology (2012), 2, 2375-2382.  Alegria's group showed that rhenium compounds were more active for the oxidation of cyclic (4, 5 and 6-membered) rings than the acyclic ketones. Rhenium complexes bearing N- or oxo-ligands were used. This is an example of homogenous catalysis. Applied Catalysis A: General (2012), 443-44, 27-32. (Copyright: HARINDRAN NAMASIVAYAM, 2002-2013) 15

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