Ruthenium-Catalyzed Cycloaddition between Propargylic Alcohols

Me, nPr, iPr) and [Cp*RuCl(µ2-SiPr)2RuCp*(OH2)]OTf (OTf ) OSO2CF3) promote the cycloaddition between propargylic alcohols and cyclic 1,3-dicarbonyl ...
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Ruthenium-Catalyzed Cycloaddition between Propargylic Alcohols and Cyclic 1,3-Dicarbonyl Compounds via an Allenylidene Intermediate Yoshiaki Nishibayashi,*,† Masato Yoshikawa,† Youichi Inada,† Masanobu Hidai,‡ and Sakae Uemura*,† Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, and Department of Materials Science and Technology, Faculty of Industrial Science and Technology, Tokyo University of Science, Noda, Chiba 278-8510, Japan [email protected]; [email protected] Received November 28, 2003

Thiolate-bridged diruthenium complexes such as [Cp*RuCl(µ2-SR)2RuCp*Cl] (Cp* ) η5-C5Me5; R ) Me, nPr, iPr) and [Cp*RuCl(µ2-SiPr)2RuCp*(OH2)]OTf (OTf ) OSO2CF3) promote the cycloaddition between propargylic alcohols and cyclic 1,3-dicarbonyl compounds to give either the corresponding 4,6,7,8-tetrahydrochromen-5-ones or 4H-cyclopenta[b]pyran-5-ones in high yields with complete regioselectivity. This catalytic cycloaddition provides a simple and one-pot synthetic protocol for a variety of substituted chromenones and cyclopenta[b]pyranones. Introduction Quite recently, we disclosed the ruthenium-catalyzed efficient propargylic alkylation of propargylic alcohols with carbon-centered nucleophiles such as ketones, β-diketones, and silyl enol ethers to give the corresponding propargylic alkylated products in high yields with quite high regioselectivity as shown in Scheme 1 using acetone as a representative substrate.1 It is noteworthy that the reactions are catalyzed only by thiolate-bridged diruthenium complexes2 such as [Cp*RuCl(µ2-SR)2RuCp*Cl] (Cp* ) η5-C5Me5; R ) Me (1a), nPr (1b), iPr (1c)), and [Cp*RuCl(µ2-SiPr)2RuCp*(OH2)]OTf (OTf ) OSO2CF3) (1d) (Chart 1). Results of some stoichiometric and catalytic reactions indicate that this novel propargylic substitution reaction proceeds via allenylidene complexes3 as key intermediates. Although remarkable developments of the reactivity of allenylidene complexes have been attained, only a few examples of catalytic reactions via allenylidene intermediates have been reported until now.4 This novel ruthenium catalysis pro†

Kyoto University. Tokyo University of Science. (1) (a) Nishibayashi, Y.; Wakiji, I.; Ishii, Y.; Uemura, S.; Hidai, M. J. Am. Chem. Soc. 2001, 123, 3393. (b) Nishibayashi, Y.; Onodera, G.; Inada, Y.; Hidai, M.; Uemura, S. Organometallics 2003, 22, 873. (2) Thiolate-bridged diruthenium complexes (1) have been found to provide unique bimetallic reaction sites for activation and transformation of various terminal alkynes; see: Nishibayashi, Y.; Yamanashi, M.; Wakiji, I.; Hidai, M. Angew. Chem., Int. Ed. 2000, 39, 2909 and references therein. (3) For recent reviews, see: (a) Werner, H. Chem. Commun. 1997, 903. (b) Touchard, D.; Dixneuf, P. H. Coord. Chem. Rev. 1998, 178180, 409. (c) Bruce, M. I. Chem. Rev. 1998, 98, 2797. (d) Cadierno, V.; Gamasa, M. P.; Gimeno, J. Eur. J. Inorg. Chem. 2001, 571. (4) For examples of catalytic reactions via allenylidene intermediates, see: (a) Trost, B. M.; Flygare, J. A. J. Am. Chem. Soc. 1992, 114, 5476. (b) Maddock, S. M.; Finn, M. G. Angew. Chem., Int. Ed. 2001, 40, 2138. (c) Yeh, K.-L.; Liu, B.; Lo, H.-L.; Huang, H.-L.; Liu, R.-S. J. Am. Chem. Soc. 2002, 124, 6510. (d) Datt, S.; Chang, C.-L.; Yeh, K.L.; Liu, R.-S. J. Am. Chem. Soc. 2003, 125, 9294. ‡

SCHEME 1

CHART 1

vides a versatile synthetic preparative method for the propargylic alkylated compounds directly from propargylic alcohols and a variety of ketones.1 The reaction is considered to be a catalytic version of the Nicholas reaction, which is well-known for propargylic alkylation, but it needs several steps and a stoichiometric amount of Co2(CO)8 for the preparation of these compounds.5 During our continuous study on catalytic reactions via allenylidene intermediates,6 we have now found a novel reaction between propargylic alcohols and cyclic 1,3dicarbonyl compounds to give the corresponding cyclo(5) For recent reviews, see: (a) Nicholas, K. M. Acc. Chem. Res. 1987, 20, 207 and references therein. (b) Caffyn, A. J. M.; Nicholas, K. M. In Comprehensive Organometallic Chemistry II; Abel, E. W., Stone, G. A., Wilkinson, G., Eds.; Pergamon: New York, 1995; Vol. 12, Chapter 7.1. (c) Green, J. R. Curr. Org. Chem. 2001, 5, 811. (d) Teobald, B. J. Tetrahedron 2002, 58, 4133. (6) (a) Nishibayashi, Y.; Wakiji, I.; Hidai, M. J. Am. Chem. Soc. 2000, 122, 11019. (b) Nishibayashi, Y.; Inada, Y.; Hidai, M.; Uemura, S. J. Am. Chem. Soc. 2002, 124, 7900. (c) Nishibayashi, Y.; Yoshikawa, M.; Inada, Y.; Hidai, M.; Uemura, S. J. Am. Chem. Soc. 2002, 124, 11846. (d) Nishibayashi, Y.; Inada, Y.; Hidai, M.; Uemura, S. J. Am. Chem. Soc. 2003, 125, 6060. (e) Nishibayashi, Y.; Yoshikawa, M.; Inada, Y.; Milton, M. D.; Hidai, M.; Uemura, S. Angew. Chem., Int. Ed. 2003, 42, 2681. (f) Nishibayashi, Y.; Imajima, H.; Onodera, G.; Hidai, M.; Uemura, S. Organometallics 2004, 23, 26. 10.1021/jo0357465 CCC: $27.50 © 2004 American Chemical Society

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Published on Web 04/14/2004

Ruthenium-Catalyzed Cycloaddition TABLE 1. Cycloaddition between Propargylic Alcohol (2) and 1,3-Cyclohexanedione (3a)a

run

R

catalyst

1 2c 3 4 5 6 7 8 9 10 11

Ph (2a) Ph (2a) Ph (2a) Ph (2a) Ph (2a) p-MeC6H4 (2b) p-ClC6H4 (2c) p-MeOC6H4 (2d) p-CF3C6H4 (2e) 2-naphthyl (2f) Ph2CdCH (2g)

[Cp*RuCl(µ2-SMe)2Cp*RuCl] (1a) [Cp*RuCl(µ2-SMe)2Cp*RuCl] (1a) [Cp*RuCl(µ2-SnPr)2Cp*RuCl] (1b) [Cp*RuCl(µ2-SiPr)2Cp*RuCl] (1c) [Cp*RuCl(µ2-SiPr)2Cp*Ru(OH2)]OTf (1d)d [Cp*RuCl(µ2-SMe)2Cp*RuCl] (1a) [Cp*RuCl(µ2-SMe)2Cp*RuCl] (1a) [Cp*RuCl(µ2-SMe)2Cp*RuCl] (1a) [Cp*RuCl(µ2-SMe)2Cp*RuCl] (1a) [Cp*RuCl(µ2-SMe)2Cp*RuCl] (1a) [Cp*RuCl(µ2-SMe)2Cp*RuCl] (1a)

isolated yield of 4 [%] 4a, 93 (>95)b 4a, (83)b 4a, (88)b 4a, (20)b 4a, (25)b 4b, 91 4c, 99 4d, 94 4e, 86 4f, 98 4g, 87

a All of the reactions between 2 (0.10 mmol) and 3a (0.50 mmol) were carried out in the presence of catalyst (0.005 mmol) and NH BF 4 4 (0.010 mmol) in ClCH2CH2Cl (3 mL) at 60 °C for 1 h. b GLC yield. c At room temperature for 1 h. d In the absence of NH4BF4.

SCHEME 2

addition products such as 4,6,7,8-tetrahydrochromen-5ones (Scheme 2) and 4H-cyclopenta[b]pyran-5-ones in high yields with complete regioselectivity. This catalytic cycloaddition provides a simple and one-pot synthetic protocol for a variety of substituted chromenones and pyranones. We describe here the results of the unprecedented cycloaddition catalyzed only by thiolate-bridged diruthenium complexes. Results and Discussion Treatment of 1-phenyl-2-propyn-1-ol (2a) with 1,3cyclohexanedione (3a) in the presence of 1a (5 mol %) and NH4BF4 (10 mol %) in 1,2-dichloroethane at 60 °C for 1 h afforded 4-phenyl-4,6,7,8-tetrahydrochromen-5one (4a) in 93% isolated yield (>95% GLC yield) (Table 1; run 1). The molecular structure of 4a was unambiguously clarified by X-ray analysis. Neither other products nor regioisomers of 4a were detected by GLC and 1H NMR. The reaction proceeded quite smoothly even at room temperature for 1 h, with 4a being obtained in 83% GLC yield (Table 1; run 2). The kind of a bridging thiolato ligand in the diruthenium complex was found to have a strong influence on the catalytic activity. Thus, the complex bearing a sterically demanding SiPr group [Cp*RuCl(µ2-SiPr)2RuCp*Cl] (1c) exhibited only low catalytic activity, while the complex bearing a SnPr group [Cp*RuCl(µ2-SnPr)2RuCp*Cl] (1b) showed almost the same catalytic activity as 1a (Table 1; runs 3 and 4). The catalytic activity of cationic complexes7 such as [Cp*RuCl(µ2-SiPr)2RuCp*(OH2)]OTf (1d) was similar to that of the neutral complexes (Table 1; run 5). Other di- and monoruthenium complexes such as [Cp*RuCl(PPh3)2], [RuCl2(PPh3)3], [RuCl2(p-cymene)]2, [(indenyl)RuCl(PPh3)2], and [Cp*RuCl(µ2-Cl)2RuCp*Cl] were ineffective (7) (a) Inada, Y.; Nishibayashi, Y.; Hidai, M.; Uemura, S. J. Am. Chem. Soc. 2002, 124, 15172. (b) Nishibayashi, Y.; Inada, Y.; Hidai, M.; Uemura, S. Angew. Chem., Int. Ed. 2003, 42, 1495.

for this catalytic cycloaddition. The use of various propargylic alcohols resulted in the formation of the corresponding 4-aryl- and 4-alkenyl-substituted 4,6,7,8-tetrahydrochromen-5-ones (4b-g) in excellent yields with complete regioselectivity (Table 1; runs 6-11). Unfortunately, the reactions of 1-cyclohexyl-2-propyn-1-ol and 1,1-diphenyl-2-propyn-1-ol with 3a did not proceed at all. Reactions of 2a with other cyclic and acyclic 1,3diketones were investigated in the presence of 1a (5 mol %) and NH4BF4 (10 mol %) in 1,2-dichloroethane at 60 °C for 1 h. Typical results are shown in Table 2. 7,7Dimethyl-4-phenyl-4,6,7,8-tetrahydrochromen-5-one (4h) was formed in high yield in the reaction of 2a with 5,5dimethyl-1,3-cyclohexanedione (3b) (Table 2; run 1). The reaction of 2a with 1,3-cyclopentanedione (3c) gave 4-phenyl-6,7-dihydro-4H-cyclopenta[b]pyran-5-one (4i) in 98% isolated yield (Table 2; run 2). In sharp contrast, only a propargylic alkylated compound (7a or 7b1a) was obtained selectively in moderate yield when the reaction of 2a with 1,3-cycloheptanedione (3d) or acetylacetone (3e) was carried out under the same reaction conditions (Table 2; runs 3 and 4). Next, reactions of propargylic alcohols with cyclic β-keto esters were similarly examined. The reaction of 2a with tetronic acid (tetrahydrofuran-2,4-dione) (3f) in the presence of 1a (5 mol %) at 60 °C for 1 h gave 4-phenyl-4,7-dihydrofuro[3,4-b]pyran-5-one (4j) in 83% isolated yield with complete regioselectivity (Table 2; run 5). The molecular structure of 4j was unambiguously clarified by X-ray analysis. The corresponding 4,7-dihydrofuro[3,4-b]pyran-5-ones were obtained from various aryl- and alkenyl-substituted propargylic alcohols (4km) in high yields (Table 2; runs 6-8). A β-keto ester with six-membered ring, 4-hydroxycoumarin (3g), reacted with 2a under the same reaction conditions to afford 4-phenyl4H-pyrano[3,2-c]chromen-5-one (4n) in an excellent yield without the formation of other isomers (Table 2; run 9). Interestingly, the reaction of 2a with an acyclic β-keto ester, methyl acetoacetate (3h), afforded the corresponding propargylic alkylated product as a mixture of two diastereoisomers (Table 2; run 10), but in low yield. It is noteworthy that the cycloaddition proceeded selectively only when cyclic 1,3-dicarbonyl compounds with five- and six-membered rings were used. On the other hand, double J. Org. Chem, Vol. 69, No. 10, 2004 3409

Nishibayashi et al. TABLE 2. Reactions of Propargylic Alcohol (2a) with Cyclic and Acyclic 1,3-Dicarbonyl Compounds (3)a

a All of the reactions of 2a (0.60 mmol) with 3 (3.00 mmol) were carried out in the presence of 1a (0.03 mmol) and NH BF (0.06 mmol) 4 4 in ClCH2CH2Cl (18 mL) at 60 °C for 1 h. b For 20 h. c 2b was used in place of 2a. d 2c was used in place of 2a. e 2g was used in place of 2a. f Two diastereoisomers were formed in an isomer ratio of 1:1. g A mixture of unidentified compounds was formed.

propargylation occurred at the R-position of meldrum’s acid (2,2-dimethyl-1,3-dioxane-4,6-dione) (3i) to give the corresponding dialkylated product in 44% isolated yield (Table 2; run 11). The reaction of 2a with dimethyl malonate (3j) gave only a mixture of unidentified products, although the starting propargylic alcohol 2a was completely consumed (Table 2; run 12). To elucidate the reaction mechanism of the cycloaddition reaction, the following stoichiometric and catalytic 3410 J. Org. Chem., Vol. 69, No. 10, 2004

reactions were investigated. Treatment of the allenylidene complex (5), which was prepared from the reaction of 1a with 1 equiv of 2a in the presence of NH4BF4 in tetrahydrofuran (THF) at room temperature for 30 min,1a with 5 equiv of 3a in 1,2-dichloroethane at 60 °C for 1 h led to the formation of 4a in 61% GLC yield (eq 1). Furthermore, the reaction of 2a with 3a in the presence of 5 mol % 5 at 60 °C for 1 h afforded 4a in 96% GLC yield. These results indicate that the cycloaddition

Ruthenium-Catalyzed Cycloaddition

of propargylic alcohols with cyclic 1,3-dicarbonyl compounds proceeds via allenylidene intermediates such as 5.8

SCHEME 3

SCHEME 4

When the reaction of 2a with 3a was carried out in the presence of 1c (5 mol %) at room temperature for 1 h in 1,2-dichloroethane, the corresponding propargylic alkylated product (6a)9 was isolated in 28% yield together with a small amount of 4a (eq 2),

while the treatment of 6a in the same solvent in the presence of 1a (5 mol %) at 60 °C for 1 h gave 4a in 65% isolated yield (eq 3).

dicarbonyl compounds to afford the corresponding chromen-5-ones and pyran-5-ones in high to excellent yields with high regioselectivity. Some mechanistic studies indicate that the catalytic cycloaddition proceeds via allenylidene intermediates. This novel catalytic reaction also provides a simple and efficient one-pot synthetic protocol for a new type of skeleton of substituted chromenones and pyranones.

Experimental Section

These results indicate that the catalytic cycloaddition proceeds via an initial propargylic alkylation. On the basis of these findings, a pathway for this cycloaddition is proposed in Scheme 3. The first step is the nucleophilic attack of the carbon atom of 2-position of 1,3-cyclohexanedione to the Cγ atom of the allenylidene complex A to give a vinylidene complex B,10 which is transformed into an alkenyl complex C by an intramolecular nucleophilic attack of the oxygen atom of hydroxyl group of an enol to the CR atom of B.11,12 In the case of the reaction of 2a with an acyclic β-diketone 3e in the presence of 1a, the hydrogen bonding in D may inhibit a nucleophilic attack of the oxygen atom, leading to the formation of only the propargylic alkylated compound (Scheme 4). Thus, the formation of a rigid structure, which facilitates the nucleophilic attack of the oxygen atom in the vinylidene complex B, is considered to be a driving force to promote the cycloaddition. Conclusion We have now found a novel ruthenium-catalyzed cycloaddition between propargylic alcohols and cyclic 1,3(8) (a) Esteruelas, M. A.; Go´mez, A. V.; Lo´pez, A. M.; On˜ate, E. Organometallics 1998, 17, 3567. (b) Bernad, D. J.; Esteruelas, M. A.; Lo´pez, A. M.; Oliva´n, M.; On˜ate, E.; Puerta, M. C.; Valerga, P. Organometallics 2000, 19, 4327. (9) White solid. 1H NMR δ 1.90-2.00 (m, 2H), 2.04 (s, 1H), 2.382.52 (m, 4 H), 2.57 (d, 1H, J ) 2.5 Hz), 5.49 (d, 1H, J ) 2.5 Hz), 7.197.32 (m, 3H), 7.39-7.42 (m, 2H). (10) Esteruelas, M. A.; Go´mez, A. V.; Lo´pez, A. M.; Modrego, J.; On˜ate, E. Organometallics 1997, 16, 5826. (11) (a) Trost, B. M.; Rhee, Y. H. J. Am. Chem. Soc. 2002, 124, 2528. (b) Trost, B. M.; Rhee, Y. H. J. Am. Chem. Soc. 2003, 125, 7482. (12) Gulias, M.; Rodriguez, J. R.; Castedo, L.; Mascaren˜as, J. L. Org. Lett. 2003, 5, 1975.

Synthesis of Substrates. Thiolate-bridged diruthenium complexes2 (1) and the allenylidene complex1a (5) were prepared according to our previous procedures. Propargylic alcohol (2a) was a commercial product. Other propargylic alcohols were prepared by the reactions of the corresponding aldehydes with ethynylmagnesium bromide. Ruthenium-Catalyzed Cycloaddition between Propargylic Alcohols and Cyclic 1,3-Dicarbonyl Compounds. A typical experimental procedure for the reaction of 1-phenyl2-propyn-1-ol (2a) with 1,3-cyclohexanedione (3a) catalyzed by [Cp*RuCl(µ2-SMe)2RuCp*Cl] (1a) is described below. In a 20 mL flask were placed 1a (19 mg, 0.03 mmol) and NH4BF4 (6 mg, 0.06 mmol) under N2. Anhydrous ClCH2CH2Cl (15 mL) was added, and then the mixture was magnetically stirred at room temperature. After the addition of 2a (79 mg, 0.60 mmol) and 3a (336 mg, 3.00 mmol), the reaction flask was kept at 60 °C for 1 h. The solvent was concentrated under reduced pressure by an aspirator, and then the residue was purified by TLC (SiO2) with EtOAc-hexane (1/9) as an eluent to give 4-phenyl-4,6,7,8-tetrahydrochromen-5-one (4a) as yellow crystals, 93.0-94.0 °C (126 mg, 0.56 mmol, 93% yield). 4-Phenyl-4,6,7,8-tetrahydrochromen-5-one (4a): 1H NMR (270 MHz, CDCl3) δ 1.90-2.02 (m, 2H), 2.28-2.33 (m, 2H), 4.34 (d, 1H, J ) 4.6 Hz), 5.16 (dd, 1H, J ) 4.6 and 5.8 Hz), 6.48 (d, 1H, J ) 5.8 Hz), 7.14-7.28 (m, 5H). 13C NMR (67.5 Hz, CDCl3) δ 20.3, 27.6, 33.8, 37.0, 109.3, 113.7, 126.2, 127.8, 128.1, 137.9, 145.0, 165.9, 197.0. IR (KBr, cm-1) 1609 (CdC), 1651 (CdC), 1676 (CdO). Anal. Calcd for C15H14O2: C, 79.62; H, 6.24. Found: C, 79.34; H, 6.33. Spectroscopic data and isolated yields of other products are as follows. 4-(4-Methylphenyl)-4,6,7,8-tetrahydrochromen-5-one (4b): Yield 91%. Colorless crystals, 106.2-107.2 °C. 1H NMR δ 1.89-1.99 (m, 2H), 2.28 (s,3H), 2.29-2.33 (m, 2H), 2.452.51 (m, 2H), 4.30 (d, 1H, J ) 4.7 Hz), 5.15 (dd, 1H, J ) 4.7 Hz and J ) 6.0 Hz), 6.48 (d, 1H, J ) 6.0 Hz), 7.07 (d, 2H, J ) 8.1 Hz), 7.18 (d, 2H, J ) 8.1 Hz). 13C NMR δ 20.1, 20.9, 27.4, 33.3, 36.9, 109.4, 113.9, 127.8, 128.9, 135.8, 137.8, 142.3, 165.9, 197.2. Anal. Calcd for C16H16O2: C, 79.97; H, 6.71. Found: C, 79.84; H, 6.71. 4-(4-Chlorophenyl)-4,6,7,8-tetrahydrochromen-5-one (4c): Yield 99%. White solid, 104.0-104.5 °C. 1H NMR δ 1.902.01 (m, 2H), 2.28-2.34 (m, 2H), 2.47-2.53 (m, 2H), 4.31 (d,

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Nishibayashi et al. 1H, J ) 4.7 Hz), 5.13 (dd, 1H, J ) 4.7 Hz and J ) 6.0 Hz), 6.51 (d, 1H, J ) 6.0 Hz), 7.23 (s, 4H). 13C NMR δ 20.1, 27.4, 33.3, 36.8, 108.8, 113.4, 128.2, 129.4, 132.0, 138.3, 143.6, 166.2, 197.2. Anal. Calcd for C15H13ClO2: C, 69.10; H, 5.03. Found: C, 69.13; H, 5.09. 4-(4-Methoxyphenyl)-4,6,7,8-tetrahydrochromen-5one (4d): Yield 94%. Colorless solid, 92.2-93.5 °C. 1H NMR δ 1.89-1.97 (m, 2H), 2.28-2.33 (m, 2H), 2.45-2.51 (m, 2H), 3.74 (s,3H), 4.28 (d, 1H, J ) 4.7 Hz), 5.15 (dd, 1H, J ) 4.7 Hz and J ) 6.2 Hz), 6.49 (d, 1H, J ) 6.2 Hz), 6.80 (d, 2H, J ) 8.7 Hz), 7.21 (d, 2H, J ) 8.7 Hz). 13C NMR δ 20.1, 27.4, 32.8, 36.9, 55.0, 109.4, 113.5, 114.0, 128.9, 137.4, 137.8, 158.0, 165.8, 197.3. Anal. Calcd for C16H16O3: C, 74.98; H, 6.29. Found: C, 74.70; H, 6.43. 4-(4-Trifluoromethylphenyl)-4,6,7,8-tetrahydrochromen-5-one (4e): Yield 86%. Colorless crystals, 106.2106.7 °C. 1H NMR δ 1.91-2.06 (m, 2H), 2.31-2.36 (m, 2H), 2.50-2.60 (m, 2H), 4.41 (d, 1H, J ) 4.5 Hz), 5.15 (dd, 1H, J ) 4.5 Hz and J ) 6.0 Hz), 6.54 (d, 1H, J ) 6.0 Hz), 7.41 (d, 2H, J ) 8.1 Hz), 7.53 (d, 2H, J ) 8.1 Hz). 13C NMR δ 20.3, 27.6, 34.0, 37.0, 108.6, 113.3, 124.3 (d, J ) 271 Hz). Anal. Calcd for C16H13F3O2: C, 65.30; H, 4.45. Found: C, 65.01; H, 4.50. 4-(2-Naphthyl)-4,6,7,8-tetrahydrochromen-5-one (4f): Yield 98%. Colorless crystals, 115.2-116.0 °C. 1H NMR δ 1.89-1.99 (m, 2H), 2.27-2.32 (m, 2H), 2.47-2.54 (m, 2H), 4.51 (d, 1H, J ) 4.7 Hz), 5.21 (dd, 1H, J ) 4.7 Hz and J ) 6.0 Hz), 6.54 (d, 1H, J ) 6.0 Hz), 7.36-7.47 (m, 3H), 7.71-7.80 (m, 4H). 13C NMR δ 20.2, 27.5, 34.0, 36.9, 109.2, 113.8, 125.3, 125.8, 126.5, 126.5, 127.5, 127.8, 127.9, 132.3, 133.4, 138.2, 142.5, 166.1, 197.3. Anal. Calcd for C19H16O2: C, 82.58; H, 5.84. Found: C, 82.60; H, 5.86. 4-(2,2-Diphenylvinyl)-4,6,7,8-tetrahydrochromen-5one (4g): Yield 87%. Yellow oil. 1H NMR δ 1.90-1.98 (m, 2H), 2.23-2.48 (m, 4H), 3.91 (dd, 1H, J ) 4.8 Hz and J ) 9.3 Hz), 4.87 (dd, 1H, J ) 4.8 Hz and J ) 5.7 Hz), 5.78 (d, 1H, J ) 9.3 Hz), 6.32 (d, 1H, J ) 5.7 Hz), 7.15-7.20 (m, 5H), 7.27-7.32 (m, 1H), 7.36-7.46 (m, 4H). 13C NMR δ 20.3, 27.5, 28.6, 37.0, 107.7, 113.1, 126.9, 127.1, 127.9, 128.1, 129.8, 131.3, 138.1, 139.6, 140.1, 142.0, 166.5, 197.5. Anal. Calcd for C23H20O2: C, 84.12; H, 6.14. Found: C, 84.08; H, 6.44. 7,7-Dimethyl-4-phenyl-4,6,7,8-tetrahydrochromen-5one (4h): Yield 94%. Pale yellow crystals, 84.8-85.2 °C. 1H NMR δ 1.00 (s, 3H), 1.07 (s, 3H), 2.18 (d, 2H, J ) 9.2 Hz), 2.37 (s, 2H), 4.31 (d, 1H, J ) 4.6 Hz), 5.16 (dd, 1H, J ) 4.6 Hz and J ) 5.8 Hz), 6.48 (d, 1H, J ) 5.8 Hz), 7.13-7.16 (m, 1H), 7.24-7.29 (m, 4H). 13C NMR δ 27.5, 29.0, 31.9, 34.0, 41.2, 50.7, 109.3, 112.5, 126.3, 127.8, 128.1, 137.9, 145.0, 164.2, 196.9. Anal. Calcd for C17H18O2: C, 80.28; H, 7.13. Found: C, 80.01; H, 7.08. 4-Phenyl-6,7-dihydro-4H-cyclopenta[b]pyran-5-one (4i): Yield 98%. Orange crystals, 91.8-92.2 °C. 1H NMR δ 2.35-2.38 (m, 2H), 2.60-2.64 (m, 2H), 4.29 (d, 1H, J ) 3.8 Hz), 5.13 (dd, 1H, J ) 3.8 Hz and J ) 5.8 Hz), 6.60 (d, 1H, J ) 5.8 Hz), 7.19-7.21 (m, 1H), 7.28-7.32 (m, 4H). IR (KBr, cm-1) 1618 (CdC), 1655 (CdC), 1694 (CdO). Anal. Calcd for C14H12O2: C, 79.22; H, 5.70. Found: C, 79.07; H, 5.68. 4-Phenyl-4,7-dihydrofuro[3,4-b]pyran-5-one (4j): Yield 83%. Colorless crystals, 138.1-138.3 °C. 1H NMR δ 4.35 (d, 1H, J ) 3.5 Hz), 4.73 (s, 2H), 5.20 (dd, 1H, J ) 3.5 Hz and J ) 5.9 Hz), 6.67 (d, 1H, J ) 5.9 Hz), 7.23-7.37 (m, 5H). 13C NMR δ 34.2, 65.7, 103.8, 108.3, 127.3, 127.9, 128.6, 139.3, 141.5, 152.4, 168.1. Anal. Calcd for C13H10O3: C, 72.89; H, 4.71. Found: C, 72.73; H, 4.81. 4-(4-Methylphenyl)-4,7-dihydrofuro[3,4-b]pyran-5one (4k): Yield 89%. Yellow solid, 140.2-141.0 °C. 1H NMR δ 2.31 (s, 3H), 4.29 (d, 1H, J ) 3.5 Hz), 4.60-4.67 (m, 2H), 5.15 (dd, 1H, J ) 3.5 Hz and J ) 6.0 Hz), 6.62 (d, 1H, J ) 6.0

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Hz), 7.13 (d, 2H, J ) 8.0 Hz), 7.19 (d, 2H, J ) 8.0 Hz). 13C NMR δ 20.9, 33.6, 65.5, 103.7, 108.3, 127.8, 129.2, 136.9, 138.7, 139.2, 168.2, 171.0. Anal. Calcd for C14H12O3: C, 73.67; H, 5.30. Found: C, 73.45; H, 5.32. 4-(4-Chlorophenyl)-4,7-dihydrofuro[3,4-b]pyran-5one (4l): Yield 80%. White solid, 143.0-144.0 °C. 1H NMR δ 4.33 (s, 1H), 4.70-4.72 (m, 2H), 5.13-5.18 (m, 1H), 6.65-6.69 (m, 1H), 7.23-7.33 (m, 4H). 13C NMR δ 33.5, 65.6, 103.3, 107.7, 128.7, 129.3, 133.1, 139.7, 140.1, 168.4, 170.8. Anal. Calcd for C13H9ClO3: C, 62.79; H, 3.65. Found: C, 62.79; H, 3.55. 4-(2,2-Diphenylvinyl)-4,7-dihydrofuro[3,4-b]pyran-5one (4m): Yield 87%. White solid, 143.5-144.3 °C. 1H NMR δ 3.92-3.95 (m, 1H), 4.63 (s, 2H), 4.91 (dd, 1H, J ) 3.6 Hz and J ) 6.0 Hz), 5.85 (d, 1H, J ) 9.9 Hz), 6.45 (d, 1H, J ) 6.0 Hz), 7.15-7.48 (m, 10H). 13C NMR δ 29.0, 65.6, 103.1, 107.7, 127.3, 127.4, 127.5, 127.8, 128.0, 128.3, 129.3, 139.0, 139.0, 141.5, 143.0, 168.8, 171.1. Anal. Calcd for C21H16O3: C, 79.73; H, 5.10. Found: C, 79.52; H, 5.19. 4-Phenyl-4H-pyrano[3,2-c]chromen-5-one (4n): Yield 97%. Colorless crystals, 152.0-152.5 °C. 1H NMR δ 4.51 (d, 1H, J ) 4.6 Hz), 5.32 (dd, 1H, J ) 4.6 Hz and J ) 6.1 Hz), 6.75 (d, 1H, J ) 6.1 Hz), 7.17-7.39 (m, 7H), 7.46-7.52 (m, 1H), 7.77-7.80 (m, 1H). 13C NMR δ 35.3, 103.5, 108.7, 114.1, 116.5, 122.5, 123.9, 126.9, 128.2, 128.3, 131.7, 137.9, 143.3, 152.3, 155.4, 161.2. Anal. Calcd for C18H12O3: C, 78.25; H, 4.38. Found: C, 78.11; H, 4.44. 2-(1-Phenylpropyn-2-yl)cycloheptane-1,3-dione (7a): Yield 34%. Colorless crystals, 115.1-115.5 °C. 1H NMR δ 1.75-1.90 (m, 2H), 2.05-2.16 (m, 2H), 2.22 (d, 1H, J ) 2.4 Hz), 2.30-2.35 (m, 2H), 2.56-2.69 (m, 2H), 4.53 (d, 1H, J ) 8.7 Hz), 4.59 (dd, 1H, J ) 2.4 Hz and J ) 8.7 Hz), 7.19-7.31 (m, 3H), 7.35-7.39 (m, 2H). 13C NMR δ 24.7, 24.9, 34.4, 44.5, 44.6, 71.6, 72.3, 83.9, 127.3, 128.3, 128.5, 138.2, 202.8, 203.3. IR (KBr, cm-1) 1697 (CdO), 1724 (CdO), 2115 (CtC), 3280 (tC-H). Anal. Calcd for C16H16O2: C, 79.97; H, 6.71. Found: C, 79.83; H, 6.75. 2-Acetyl-3-phenylpent-4-ynoic Acid Methyl Ester (7c): Yield 24%. A colorless oil. Two diastereoisomers with a ratio of 54:46. 1H NMR δ 1.96 and 2.37 (s each, 3H), 2.29 and 2.30 (d each, 1H, J ) 2.4 Hz), 3.51 and 3.78 (s each, 3H), 3.95 and 4.01 (d each, 1H, J ) 10.5 Hz), 4.40 and 4.44 (dd each, 1H, J ) 2.4 Hz and J ) 10.5 Hz), 7.24-7.38 (m, 5H). 13C NMR δ 29.9 and 30.7, 36.8 and 36.9, 52.3 and 52.7, 65.9 and 66.3, 72.0 and 72.6, 82.7 and 83.0, 127.8, 128.0, 128.2, 128.7, 128.8, 137.5, 167.0 and 167.4, 200.1 and 200.4. IR (neat, cm-1) 1721 (CdO), 1748 (CdO), 2117 (CtC), 3285 (tC-H). Anal. Calcd for C14H14O3: C, 73.03; H, 6.13. Found: C, 73.04; H, 6.14. 2,2-Dimethyl-5,5-bis(1-phenylpropyn-2-yl)-[1,3]dioxane4,6-dione (7d): Yield 44%. White crystals, 160.7-161.2 °C. 1 H NMR δ 0.46 (s, 6H), 2.65 (d, 2H, J ) 2.7 Hz), 5.10 (d, 2H, J ) 2.7 Hz), 7.27-7.35 (m, 6H), 7.40-7.43 (m, 4H). 13C NMR δ 28.2, 44.7, 63.4, 74.8, 80.3, 106.1, 128.6, 129.0, 129.6, 135.0, 164.4. IR (KBr, cm-1) 1744 (CdO), 1767 (CdO), 2119 (CtC), 3267 (tC-H), 3296 (tC-H). Anal. Calcd for C24H20O4: C, 77.40; H, 5.41. Found: C, 77.41; H, 5.42.

Acknowledgment. This work was supported by a Grant-in-Aid for Scientific Research for Young Scientists (A) (No. 15685006) from the Ministry of Education, Culture, Sports, Science and Technology, Japan. Supporting Information Available: Tables and figures giving crystallographic data for 4a and 4j; crystallographic data are also available as CIF files. This material is available free of charge via the Internet at http://pubs.acs.org. JO0357465