Baeyer-Villiger Oxidation of lndan-I -Ones Monitoring of the Reaction by VPC and IR Spectroscopy Elie Stephan Ecoie Nationale Superieure d e Chirnie de Paris, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05, France A similar treatment can be applied for the oxidation of indanone (R = H). This result is in agreement with the literature (11,showing that the migratory aptitude during Baeyer-Villiger type rearrangements is aryl > primarily alkyl.
Baeyer-Villiger oxidation of cyclic ketones is a classic synthetic method for lactones ( I ) . A few years ago this Journal puhlished a n article on intramolecular esterification a s a route to lactones (2)but no experiment using the Baeyer-Villiger reaction i s reported therein. Indan-l-ones are oxidized either by CF3C03H, which is prepared from TFAA and 30% commercial HzOz (31, or by MCPBA in refluxing dichloroethane (4). The oxidation of 3-methyl-indan-l-one i s a part of a multistep synthesis that can include the preparation of chiral products (5).A shorter experiment descrihes the qualitative monitoring of the oxidation of commercially available indan-l-one to dihydrocoumarin by two standard analytical techniques, vapor phase chromatography, and IR spectroscopy. The TFAAiHzOz method is a more efficient way for synthesizing the dihydrocoumarins. The MCPBAmethod has been used for monitoring of the oxidation of the indan-l-one. Identification of the Product Obtained The Baeyer-Villiger reaction proceeds via an oxygen insertion, which, in the case of a cyclic unsymmetrical ketone, can lead to two lactone isomers. 'H NMR spectroscopy permits easy identification of the product obtained, chiefly by examining the chemical shift of the methylene situated either a to the carbonyl group in 2 or a to the oxygen in 3. The figure shows the spectrum of the crude reaction product obtained from the oxidation of indanone 1 (R = Me) by CF3C03H. (This indanone is ohtained by t h e following reactions: Michael addition of PhzCuMgBr to ethyl crotonate, or to a chiral crotonate for asymmetric synthesis (51,saponification of the adduct followed by intramolecular acylation of the acid chloride thus obtained.) T h e methylene appears a s the AB part of a n ABX type spectrum, because the two protons are diastereotopic, with a n approximate chemical shift of 2.7 ppm (the fine splitting is observed with a 200 MHz NMR). 0 Thus, the student can take advantage of the spectrum simula- (R tor published by this Journal ( 6 ) for acyclic molecules equivalent to 2 and 3, viz. phenyl3-phenylh u t a n o a t e 2' a n d 2-phenylpropyl benzoate 3', to evaluate t h e c h e m i c a l s h i f t of t h e methylene protons in the two isomers. The simulated spectra predict doublet-type s i g n a l s for these methylenes, because the simulator does not see the dias[I( + , tereotopic phenomenon with 6 = ,, 2.6 DDm for 2' and 6 = 4.5 DDm for 3'. I t , t h u s , a p p e a r s t h a t t h e - , product formed during oxidation *.a 7.3 1.0 .
Oxidation of lndan-l-One and Monitoring of the Reaction Indanone 1(R = HI is oxidized completely to 2 in 2 3 h a t RT bv ~eroxvtrifluoroaceticacid. while the reaction ~roceeds to a b i i t 75% completion in 5 h when using M C P B A ~refluxine dichloroethane (see ex~erimentalsection). These results I t:fli,ctiw! oxidant than cl&lr show that C F ~ C O is~ n~ more hlCPRA fbr this reaction 1I. Monirorine of the rcaction w a s done for the oxidation of the indanone h i MCPBA. VPC Analysis
After a sample has been removed and treated using the method described i n the experimental section, an injection is made onto an SE30 column (10% wt.) a t 180 "C (widebore column, l = 3 m ;D = 4 mm). The student should have injected the starting materials and final products beforehand so that the peaks can be identified when the reaction mixture is analyzed. The chromatograms show a n increasing appearance of the product 2 (retention time = 200 s) with decreasing amounts of the starting material 1 (r.t. = 144 s). lR analysis The same sample i s used to record a n IR spectrum as described i n the experimental section. The carbonyl vibra-
4 a. q0
,
..
1,'
..
is 3,4-dihydr0coumarin 2.
1142
0
2
1'
6
of
andlor
'H NMR
Journal of Chemical Education
.
0
3
5.5
dl
,
,
5.0
1.3
r. , .
1.0 "W
,
I i .T. 1.1
,
4
...L, ....,~. - ----~1.0
i.i
..a
1.3
::o
spectrum (Bruker AC 200) for oxidation product of indanone 1 (R = Me) with CF,CO,H
,
0:0
tions give two well-separated bands (CO a t 1710 em-' for indanone 1; CO a t 1770 c n i ' for dihydrocoumarin 2). The monitoring experiment can he undertaken as part of a lahoratorv session. I t ~ r o v i d e sthe student with the ODportunity not only to perform a synthesis not commonly carried out i n a n undergraduate laboratory, hut also to apply classic analytical methods to follow the progress of the reaction. The wider ~roiect.which involves the ~ r i o svnr thesis of 3-~e-indan:l-&1e,'has been made by a student of advanced class. Experimental Procedures Oxidation by Peroxytrifluoroacetic Acid Caution: When using peroxytrifluoroacetic acid, work under the hood.
Amethod described in the literature (3)was adapted. 0.4 mL 30% Hz02 is mixed with 2 mL dichloromethane. After cooling in a n ice water bath. 2 mL trifluoroacetic anhvdride added dropwise to the'mixture, while using a magnetic stirrer and maintaining the temperature below 10 "C (partial decomposition of HzOz or peracid seems to occur when the temperature rises higher than r.t. and the yield is decreased). Stirring is continued for 30 min while the medium is allowed to return to room tem~erature.This Deracid solution is then added to a solution df 2 mmol indaAne in 2 mL dichloromethane at room temperature, and stirred for 2-3 h. The excess peracid is neutralized by the addition of 10% sodium bisulfite. The medium is diluted with ether, and the organic phase is washed successively with 10% sodium
carbonate and water. ARer drying and concentration the crude product is obtained with more than 90% yields. An NMR spectrum is recorded (see figure). Oxidation with MCPBA
0.65 g (5 mmol) indan-l-one is dissolved in 10 mL dichloroethane. 0.1 g paratolueuesulfonic acid and 3.75 g 5060% MCPBA (Aldrich) are added and brought to reflux. 3.75 g peracid are added after 3 h and reflux continued for a further 2 h. The medium is then treated as described above. Analyses
After time t , 1mL of the preceding solution i s taken and dropped into 10% sodium bisulfite. I t is then diluted with 10 mL ether, decanted, and the organic phase washed with 10% carbonate, then water. Finally, i t is dried and concentrated, leaving a little solvent to facilitate VPC injection. The residual ether is then evaporated for recording an IR spectrum in perchlorohutadiene. Literature Cited 1. March, J. Aduonczd Opganic Chemistry, 3rd ed.: J.Wiiey & Sons: New York. 1985, p W"
2. MeGahey. L. J Chem. Educ 1986.63. 1101. 3. Anastasia, M.:Allevi, P: Ciuffrcda.P.: Fiecehi. A,: Sca1a.A. J. Org. Chem 1985. 50, 321. 4. kwia.S. N.In Oridolion; Augustine,R. L.. Ed.:M . Dekker: New York, 1969: Vol. 1, Chapter 5. 5. Stephsn, E.: Rochec R.:Aubouei, J.:Paurcelot, G.:Cresson, P. lbfrohsdron :Asymmetry 1894.5.41. 6. Black.KA. J Chem. Educ.:Soiluom 19%. Val. IIC i l i , 11.
Volume 72
Number 12 December 1995
1143
