Organometallics 1996, 14, 5438-5441
5438
Notes Nickel-CatalyzedCarbonylation of a-Keto Alkynes under Phase Transfer Conditions Henri Arzoumanian,*l+ Magali Jean,? Didier Nuel,? Armando Cabrera,$ Jose Luis Garcia Gutierrez,$ and Noe Rosa& Ecole Nationale SupLrieure de Synthtse, de ProcLdLs et d'IngLniLrie Chimiques d'Aix-Marseille, URA du 1410, Universitt? d'Aix-Marseille III, 13397 Marseille, France, and Instituto de Quimica, Universidad Nacional Autonoma de Mexico, 04510 Mexico, D.F., Mexico Received June 9, 1995@ Summary: a-Keto alkynes are carbonylated in the presence of Ni(CN)2 under phase transfer conditions (toluene, 5 N NaOH, tetrabutylammonium bromide) to give either unsaturated hydroxybutyrolmtonesor 2-alkylidene 3-keto carboxylic acids depending on the presence or absence of an a-Hon the carbon a to the alkynyl group. This is rationalized, in the second case, by a rearrangement following abstraction of this a-Hby base. A rearrangement to a n allenic intermediate prior to carbonylation is excluded. Introduction
Transition-metal-mediated carbonylation reactions have been of great interest in recent years, and they continue t o arouse increasing interest.' Among the numerous metals used, nickel cyanide, under transfer conditions, has been shown to be a versatile catalytic system.2 A large variety of substrates have been carbonylated either stoichiometrically or catalytically, and the synthesis of lactones or their hydrolysis products, y-hydroxy or y-keto carboxylic acids, has been one of the most studied areasel Five-membered lactones can thus be readily obtained by carbonylation of allylic alcohols, under oxygen, in the presence of catalytic quantities of Pd(I1) and CU(II)~ or with a ruthenium ~ a t a l y s t .They ~ can also be prepared under pressure of CO/H2 from allylic esters with C02(CO)85or from alkynes and iodomethane in the presence of Mn(CO)sBr.6 Unsaturated five- or six-membered lactones can also be obtained through various synthetic routes. a-Methylene lactones are obtained by carbonylation of vinyl halides in the presence of stoichiometric quantities of Ni(PPh3)2(C0)2718 or from ethynyl alcohols by carbonylation either stoichiometricallywith Ni(C0h9 Universit6 d'Aix-Marseille 111. Universidad Nacional Autonoma de Mexico. @Abstractpublished in Advance ACS Abstracts, October 1, 1995. (1)Colquhoun, H. M.; Thompson, D. J.; Twigg, M. V. Carbonylation: Direct Synthesis of Carbonyl Compounds; Plenum: New York, 1991. (2)Job, F.;Alper, H. Organometallics 1986,4,1775. (3)Alper, H.; Leonard, D. Tetrahedron Lett. 1986,26,5639. (4)Kondo, T.;Kodoi, K.; Mitsudo, T.; Watanabe, Y. J . Chem. SOC., Chem. Commun. 1994,755. ( 5 ) Falbe, J.; Huppes, N.; Korte, F. Chem. Ber. 1964,97,863. (6)Wang, J.-X.; Alper, H. J . Org. Chem. 1986,51,273. (7) Semmelhack, M. F.; Brickner, S. J. J.Am. Chem. SOC.1981,103, 3945. (8)Semmelhack, M. F.; Brickner, S. J. J . Org. Chem. 1981,46,1723. (9)Jones, E.R. H.; Shen, T. Y.; Whiting, M. C. J.Chem. SOC.1960, 230. +
or catalytically with PdC12.1°-12 Ethynyl alcohols also give 2(5IdIfuranones upon carbonylation using Pd(CH3CN)z(PPh&(BF& as ~ata1yst.l~Recently, Pd(C1)2(PPh&-catalyzed carbonylation of either an internal alkyne-organic halide mixture or (Z)-P-iodoenones was reported to give the corresponding 2-butenolides or the (2)-3-alkylidene-2-butenolides, depending on the substrate structure.14 Another way to attain unsaturated lactones, although more specific t o aromatic lactones, is carbonylating o-halobenzyl alcohols in the presence of Pd(I1) and tertiary amines.15 Unsaturated hydroxybutyrolactones have been obtained through Co(CO)4-catalyzed carbonylation of alkynes in the presence of alkyl iodidel6-l8 or by double carbonylation of styrene oxide.18 Finally, an unsaturated ketobutyrolactone was the result of a double carbonylation of halodienes catalyzed by Ni(CN)2 under phase transfer conditions.lg In our pursuit of studying carbonylation reactions of substituted alkynes, we report the case of a-keto alkynes which afford, in the presence of Ni(CN)2 under phase transfer conditions, unsaturated hydroxybutyrolactones or 2-alkylidene 3-keto carboxylic acids, depending on the presence or absence of an a-H on the group attached to the alkynyl function. Results and Discussion
Nickel-catalyzed carbonylations of alkynols20,21or alkynyl h a l i d e ~ ~ Ohave - ~ ~been reported t o give monoor dicarboxylated products. When they are performed (10)Norton, J. R.; Shenton, K. E.; Schwartz, J . Tetrahedron Lett. 1976,51. (11)Murray, T.F.;Norton, J . R. J . A m . Chem. SOC.1979,101,4107. (12)Murray, T.F.; Samsel, E. G.; Varma, V.; Norton, J . R. J . Am. Chem. SOC.1981,103,7520. (13)Matsushita, K.; Komori, T.; Oi, S.; Inoue, Y.Tetrahedron Lett. 1994,35,5889. (14)Copbret, C.; Sugihara, T.; Wu, G.; Shimoyama, I.; Negishi, E.I. J . Am. Chem. SOC.1996,117,3422. (15)Cowell, A.; Stille, J . K. J.Am. Chem. SOC.1980,102,4193. (16)Alper, H.; Currie, J. K.; Des Abbayes, H. J . Chem. SOC.,Chem. Commun. 1978,311. (17)Heck, R. F.J.A m . Chem. SOC.1964,86,2819. (18)Arzoumanian, H.; Petrignani, J. F. Tetrahedron Lett. 1986,27, 5979. (19)Alper, H.; Vasapollo, G. Tetrahedron Lett. 1989,30,2617. (20)Jones, E.R. H.; Whitham, G. H.; Whiting, M. C. J . Chem. SOC. 1967,4628. (21)Satyanarayana, N.; Alper, H. Organometallics 1991,10,804. Cochini, F.; Nuel, D.; Petrignani, J . F.; Rosas, (22)Arzoumanian, H.; N. Organometallics 1992,11, 493. (23)Arzoumanian, H.; Cochini, F.; Nuel, D.; Rosas, N. Orgunometallics 1993,12,1871.
0 1995 American Chemical Society
Notes
Organometallics, Vol. 14,-No. 11, 1995 5439 Table 1. Carbonylation of a-Keto Alkynes" 0
R-CGC-C,
entry no.
//
R'
R
R
3 4
25 80
CH3 (1) C(CH3)3 (5) CH3 ( 8 ) C(CH3h (10)
C6H5 C6H5 C4H9 C4H9
1 2
temp, "C
55 80
time,
product distribn
yield,b %
h
6
78
24 24 15
35c 53
Furanone
acid
100 (2) 41 (6)
59 (7) 100 (9) 100 (11)
67
Reaction conditions: keto alkyne (10 mmol), toluene (25 mL), 5 N NaOH (25 mL), Ni(CN)y4H20 (1.0 mmol), tetrabutylammonium bromide (0.3 mmol), CO (1atm). Isolated yields. Based on 50% conversion. a
in the presence of base under phase transfer conditions (PTC), a nucleophilic attack by the anionic nickel catalyst onto the alkyne is thought to be the initial step,24 with the corresponding leaving group being either a nickelate or a halide ion. Considering an electron pair on a carbonyl group as being a "leaving" entity, carbonylation of a-keto alkynes with the Ni(CN)2/ PTC catalytic system should a priori result in a carboxylated product without loss of the oxygenated function. Treatment of 4-phenyl-3-butyn-2-one (1)with carbon monoxide (1 atm) and catalytic quantities of Ni(CN)2 under phase transfer conditions (toluene, 5 N NaOH, tetra-n-butylammonium bromide) afforded as the only product the unsaturated hydroxylactone (2) in 78% isolated yield.
I:
Ni(CN), / CO PhCH, ,5N NaOH
1
Ni(CO),CN
co H20
render dehydration difficult or the lower stability expected for compound 4 compared t o 2.
*
P h - C E C -C-CH,
Scheme 1. Formation of Hydroxylactone
TBAB Ph
H
4 2
3
Hydroxylactones, either saturated or not, are wellknown to undergo a rapid tautomeric equilibrium to the corresponding y-keto acid; compound 3 could have thus plausibly been expected to be observed, but its presence was not detected under the experimental conditions. This is in agreement with the ring-chain tautomerism generally observed with such y-keto a ~ i d s . ~Indeed, ~-~~ the absence of sterically demanding groups on the keto function leads almost exclusively to the cyclic tautomer. Supporting evidence for this is given by replacing the methyl group in 1 by a bulkier tert-butyl group (5). This altered somewhat the lactonization step and yielded, as expected, both the hydroxylactone (8) and the corresponding open-chain keto acid (7)28(see Table 1). A plausible mechanism for the formation of 2,6, and 7 is illustrated in Scheme 1. One other product might have been found, the dehydrated hydroxylactone 4-phenyl-1-methylene-2-butenolide (4). Its presence, again, was not detected. This could be due to either the experimental conditions that (24) Arzoumanian, H.; Choukrad, M.; Nuel, D. J.Mol. Catal. 1993, 85, 285. (25) Jones, P. R. Chem. Rev. 1963,63,461. (26) Escale, R.; Verducci, J. Bull. SOC.Chim.Fr. 1974,1203. (27) Valters, R. E.; Flitsch, W. Ring-Chain Tautomerism;Plenum Press: New York, 1985. (28) Roussel, C.; Gallo, R.; Chanon, M.; Metzger, J. Bull. SOC.Chim. Fr. 1971,1902.
In striking contrast with substrates 1 and 5, replacing the phenyl group by an a-H-containing alkyl group results in a carboxylated product in which the unsaturation has undergone a migration. Thus, the reaction of 3-odyn-2-one (8)with CO afforded as the only isolated product (53%)the unsaturated keto acid 9. None of the corresponding hydroxylactone was detected. The absence of cyclic tautomer in this case is expected, since saturated hydroxylactone rings are known to be less
9
Ni(CN), / CO
CH,(CH,),-CEC-C-CH,
c
PhCH3 ,5N NaOH 8
TBAB
a 9
Replacing the methyl group a to the keto function by a tert-butyl group (10)had, as expected, no effect, and the reaction proceeded in an analogous manner to give the corresponding unsaturated keto acid 11 (see Table 1).
Notes
5440 Organometallics, Vol. 14,No. 11, 1995
Scheme 2. Formation of Keto Acid via Allene
R=CH, R=C(CH&
8 10
I hydroxylactones or unsaturated keto acids. The structure of the final product is dependent on the nature of the substituent of the alkynyl group. Scheme 3. Formation of Keto Acid via a-Hydrogen Abstraction
L
Ni(CO),CN
Y CH,(CH2)3-C=C=C-R I
-
Ni(C0)3CN
co
HZO
H
I 3
CH,(CH,),-CH -C=CH-C-R
1< 38
O'C
b(CO)3CN
Experimental Section General Comments. Unless otherwise noted, all materials were obtained from commercial suppliers and used without further purification. NMR spectra were recorded on a Bruker AClOO or a Bruker AC200 spectrophotometer. The chemical shifts (ppm) were determined relative to (CH3)dSi. IR spectra were recorded on a Perkin-Elmer 1720X FTIR spectrometer. Thin-layer or column chromatography was performed on silica gel (Merck). Reactions were done in a 100 mL double-walled, thermostated reactor equipped with a magnetic stirrer and inlet tube for gas bubbling. The alkynyl ketones and octa3,4-dien-2-one were prepared according to published metho d ~ . ~ ~ General Procedure for the Nickel Cyanide and Phase Transfer Catalyzed Carbonylations. Toluene (25 mL) and
Two possible paths can be envisaged to explain this striking difference in selectivity between 2,6and 8,lO. The first one (Scheme 2) involves a prior rearrangement of the keto alkyne into a keto allene, followed by a carbonylation catalyzed by the nickel anion and hydroly~is.~~ The second (Scheme 3) involves an initial nucleophilic attack by the nickel catalyst at the alkynyl carbon in a manner analogous to that for substrates 1 and 5. The intermediate obtained, either before or after CO insertion into the carbon-nickel bond, undergoes a proton abstraction by base on the a-carbon of the alkyl group followed by rearrangement and lactonization t o give 12. Hydrolysis of this latter species gives the observed product. In order t o differentiate between these two possibilities, the keto allene 13 was synthesized and allowed t o react under the same reaction conditions. The reaction proceeded faster and afforded only polymeric tarry material, thus excluding the path shown in Scheme 2. In summary, a-keto alkynes, in the presence of catalytic amounts of Ni(CN)2, are carboxylated under phase transfer conditions to give either unsaturated
5 N NaOH (25 mL) were degassed and saturated with CO under atmospheric pressure before Ni(CN)y4H20 (1.0 mmol) and tetrabutylammonium bromide (0.3 mmol) were introduced, and the mixture was kept at room temperature overnight with stirring while CO was slowly (2-3 mumin) bubbled through the solution. To the yellow two-phase mixture was then added 10 mmol of substrate, Stirring and flow of CO were maintained for the desired time and at a given temperature. The treatment of the two phases was done as follows. With R = Bu or Et. The aqueous phase is acidified (pH 1) (Caution! HCN is formed). Extraction with ethyl acetate (2 x 25 mL), drying (MgS04) of the combined extracts, and rotary evaporation yielded the corresponding acids. The organic phase contained none of the acid or the corresponding lactonized hydroxyfuranone. With R = Ph and R = Me. The aqueous phase is acidified (pH 1) (Caution! HCN is formed). Extraction with ethyl acetate (2 x 25 mL), drying (MgSO4) of the combined extracts, and rotary evaporation yielded part (22%) of the hydroxyfuranone. The organic phase, upon evaporation, gave an orange oily residue, from which the hydroxyfuranone was isolated in 65% yield. It could be recrystallized from CHzCldn-pentane (l/l). With R = Ph and R' = But. The aqueous phase is acidified (pH l),(Caution! HCN is formed). Extraction with ethyl acetate (2 x 25 mL), drying (MgS04) of the combined extracts, and rotary evaporation yielded the acid 7. Evaporating the organic phase to dryness led to a n orange residue, which was purified by liquid chromatography on silica (n-pentanelethyl acetate, 85/15) to yield the hydroxyfuranone 6. 1-Phenylbut-1-yn-3-one(1):colorless liquid; bp 70 "C (0.76 mmHg); IR selected Y (cm-') 2200 (CIC), 1670 (CO); 'H NMR (100 MHz, CDC13) 6 2.31 (s, 3H, CH3), 7.35 (m, 5H, Ph), 13C{'HI NMR (25 MHz, CDC13) 6 32.8 (CH3), 88.3, 90.3 (CEC), 120.0 (Cipso), 128.7, 133.1, 130.8 (CH of Ph), 184.7 (CO).
(29)Allenic carboxylic acids have been reported to afford 2(6H)furanones.'3.
(30)Brandsma, L. Preparative Acetylenic Chemistry; Elsevier: New York, 1988.
H2O
9
or
10
12
-
-
-
Notes 3-Phenyl-5-methyl-5-hydroxy-2(5H)-furanone (2):white solid; mp 145 "C; IR selected Y (cm-') 1697 (CO); 'H NMR (200 MHz, CDC13) 6 1.67 (s,3H, CHd, 6.75 (s broad, lH, OH), 6.97 (s, lH, HC=C), 7.33 (t, 3H, H a r m & p), 7.73-7.78 (m, 2H, H ar 0 ) ; 13C(lH} NMR (50 MHz, CDCl3) 6 30.6 (CH3), 88.8 (C-OH), 132.3, 133.4, 132.5 (CH of Ph), 136.5, 137.8 (C ipso and C=CH), 151.0 (CH-C), 175.0 ((20). l-Phenyl-4,4-dimethylpent1-yn-3-one (5):colorless liquid; bp 80 "C (0.6 mmHg); IR selected Y (cm-') 2200 (CzC), 1664 (CO); 'H NMR (200 MHz, CDC13) 6 1.21 (s,9H, (CH&C), 7.35, 7.49 (m, 5H, Ph); 13C(lH}NMR (50 MHz, CDC13) 6 26.1 ((CH&C), 44.8 ((CH3)3C),85.9, 92.1 (CEC), 120.1 (c ipso), 128.6, 130.5, 132.9 (CH of Ph), 194.0 (CO). 3-Phenyl-5-( 1,l-dimethylethyl)-5-hydroxy-2(5H)-furanone (6):white solid; IR selected Y (cm-I) 1672 (CO); 'H NMR (200 MHz, DMSO-&) 6 0.98 (s, 9H, (CH&C), 5.77 (s broad, l H , OH), 7.33, 7.94 (m, 5H, Ph), 8.50 (broad s, lH, CHI; 13C('H} N M R (50 MHz, DMSO-&) 6 25.2 ((CH3)3C),37.3 ((CH&C), 90.2 (COH), 127.2, 128.2 (CH or phenyl), 131.6 (C=CH), 134.0 (C ipso), 143.9 (CH=C), 170.7 ((20). 5,5-Dimethy1-4-0~0-2-phenylhex-2-enoic acid (7):white solid; mp 120 "C; lH NMR (200 MHz, CDC13) 6 1.26 (s, 9H, (CH3)3C),7.45, 8.1 (m, 6H, Ph and CH=C); 13C(lH}NMR (50 MHz, CDC13) 6 26.3 ((CH3)3C),38.6 ((CH3)3C),127.5, 130.2 (CH of phenyl), 133.8 (C=CH), 137.0 (C ipso), 145.0 (CH=C), 170.7 (COOH), 180.9 (CO). Oct3-yn-2-one(8):colorless liquid; bp 70 "C (7.5 mmHg); IR selected Y (cm-l) 2212 (CzC), 1670 ((20); lH NMR (200 MHz, CDC13) 6 0.90 (t, 3H, CH~CHZ, 7.1 Hz), 1.39 (sext, 2H, CHzCHzCH3, 7.4 Hz), 1.53 (quint, 2H, CH2CH2CHzCH3, 6.9 Hz), 2.29 (5, 3H, CH&o), 2.34 (t, 2H, CHzC-C, 6.9 Hz); 13C(lH} NMR (50 MHz, CDC13) 6 13.4 (CH3CH21, 18.5
Organometallics, Vol. 14, No. 11, 1995 5441 (CHZCIC), 21.8 (CH&O), 29.6, 32.6 (CHz), 81.3 (CsCCHz), 93.9 (C=CCO), 184.8 (CO). 2-(2-Oxopropyl)hex-2-enoic acid (9):white solid; mp 77 "C; 'H NMR (200 MHz, CDCl3) 6 0.94 (t, 3H, CH3, 7.3 Hz), 1.44 (sect, 2H, CHzCHzCH3, 7.3 Hz), 2.05-2.21 (q, 2H, CHZCH-, 7.3 Hz), 2.20 (s,3H, CH&o), 3.43 ( s , ~ HCHzCO), , 7.14 (t, lH, CH-C, 7.3 Hz); 13C(lH}NMR (50 MHz, CDC13) 6 13.8 (CHsCHz),21.6 (CHZCH~), 29.6 (CH&O), 31.1(CHzCH=), 41.1 (CHzCO), 125.4 (C=CH), 148.7 (CH=C), 172.3 (COOH), 205.5 (CO). l,l-Dimethylnon-4-yn-3-one (10):colorless liquid; bp 80 "C (6 mmHg); IR selected v (cm-') 2211 (CzC), 1672 (CO); lH NMR (100 MHz, CDC13) 6 0.90 (t, 3H, CH~CHZ, 6.7 Hz), 1.15 (s, 9H, (CH3)3C), 1.3-1.8 (m, 4H, CHZCHZCH~), 2.35 (t, 2H, CHzCrC, 6.6 Hz); l3C(lH}NMR (25 MHz, CDCl3) 6 13.5 ( C H 3 CHz), 18.7 (CHzC=C), 22.0, 29.8 (CHz), 26.1 (CH3)3C), 44.6 (C(CH&), 78.8 (CHzCIC), 95.7 (CNXO), 194.5 (CO). 2-(2-0xo-3,3-dimethylbutyl)hex-2-enoic acid (11): white solid; 'H NMR (200 MHz, CDCl3) 6 0.92 (t, 3H, CH3, 7.3 Hz), 1.23 (5, 9H, C(CH&), 1.48 (sext, 2H, CHzCH3, 7.3 Hz), 2.07 (9, 2H, CHzCHzCH3, 7.3 Hz), 3.51 (s, 2H, CHz), 7.09 (t, lH, CH=C, 7.3 Hz); 13{lH} NMR (50 MHz, CDC13) 6 13.9 ( C H 3 CHz), 21.7 (CHsCHz), 26.5 (C(CH&), 31.2 (CH~CHZCHZ), 34.4 (CHz), 44.4 (C(CH3)3), 126.0 (C=CH), 147.7 (C=CH), 172.4 (COOH), 212.0 ((20).
Acknowledgment. This work was done under the auspices ofthe program PCP Franco-Mexicain. Financial support by CONACyT is kindly acknowledged. OM950443P
