Fluorine-Containing Synthons

Chapter 19

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Use of Trifluoroacetaldehyde Ethyl Hemiacetal in a Simple and Practical Synthesis of β-Hydroxy-β-trifluoromethylated Ketones Kazumasa Funabiki Department of Materials Science and Technology, Faculty of Engineering, Gifu University, 1-1, Yanagido, Gifu 501-1193, Japan

The reaction of trifluoroacetaldehyde ethyl hemiacetal or hydrate with an equimolar amount of enamines or imines, derived from various methyl ketones with aliphatic, aromatic, and heteroaromatic substituents, via the in-situ generation of trifluoroacetaldehyde, affording high yields of the corresponding β-hydroxy-β-trifluoromethyl ketones is described. Extended studies using chiral auxiliaries or catalyst are also discussed.

Introduction α-Trifluoromethylated alcohols are some of the most valuable compounds in organofluorine synthesis, because they can serve as the useful core system of liquid crystals (/) or antidepressants (2) imparted by a trifluoromethyl group Most syntheses of these compounds utilize the α-trifluoromethylated building blocks such as trifluoroacetaldehyde (CF CHO), its derivatives (5), and ottrifluoromethyl ketones as the starting substrates. Among them, CF CHO is especially the most attractive compound for the construction of octrifluoromethylated alcohol units. Therefore, it widely employed in Aldol (4% Mukaiyama (5), Ene (6), Friedel-Crafts (7), Morita-Baylis-Hillman reactions (#), 3

3

342

© 2005 American Chemical Society

Soloshonok; Fluorine-Containing Synthons ACS Symposium Series; American Chemical Society: Washington, DC, 2005.

343

etc. However, just before employing CF CHO, it should be generated from its hemiacetal or hydrate using an excess amount of cone, sulfuric acid at a high reaction temperature (9). Moreover, careful treatment of the aldehyde is required due to its troublesome properties such as being a gas at room temperature, highly reactive leading to self-polymerization, and extremely hygroscopic (10) (Scheme 1). 3

Ο


OH 120 °C F CÔX 3

cone. H S0 2

4

X = H, R Scheme 1. Previous method for the generation of trifluoroacetaldehyde. Therefore, it is quite important to find and develop much more convenient and environmentally-benign methods for the effective in-situ generation and tandem (asymmetric) carbon-carbon bond formation reaction, although there are some successful examples using hydrazones (5a), active methylene compounds (3d), and so on (3c, A). (Scheme 2). Reagent or

OH catalyst

Ο

Nu

OH

F CÔX 3

X = H, R

In-situ generation

Scheme 2. This article reviews our novel protocol for the effective generation of CF CHO and the simultaneous stereoselective carbon-carbon bond forming reaction leading to β-trifluoromethylated aldol units. 3

Reaction of Trifluoroacetaldehyde Ethyl Hemiacetal with Enamines or Imines Reaction with Various Enamines The reaction of trifluoroacetaldehyde ethyl hemiacetal l a with an equimolar amount of an enamine, derived from acetophenone with morpholine, at room


344

temperature in hexane for 1 h, followed by hydrolysis, produced the β-hydroxyβ-trifluoromethyl ketone 3a in 88% yield (77) (Table 1, entry 1).

Table 1. Reaction of Trifluoroacetaldehyde Ethyl Hemiacetal or Hydrate with Ënamines Derived from Various Methyl Ketones


0

Q

OH +

F CÔX

^X 1

3

2

Entry

1

Enamine R

1 2 3 4 5 6 7 8" 9

la la la la la la la la lb

2a 2b 2c 2d 2e 2f 2g 2h 2a

C

Ph 4-ΜεΟΗ4 4-MeOC H4 4-ClC H 4-N0 C H, 2-MeC H4 2-thienyl /'-Pr Ph 6

6

4

6

6

1

3

1

2

Ο

F a C ^ ^ R

hexane'

R

1a:X=Et 1b:X = H

e

OH

Temp.

Product

Yield (%)*

rt It rt rt rt rt rt rt reflux

3a 3b 3c 3d 3e 3f 3g 3h 3a

88 87 72 86 52 87 75 25 84

α

The reaction was carried out with trifluoroacetaldehyde ethyl hemiacetal la or hydrate lb (1 mmol) with enamine 2 (1 mmol) in hexane (4 ml) at ambient temperature. Yields of isolated pure products. Toluene in place of hexane was used as a solvent. A mixture of 2h and 4-(3-methylbut-l-en-2-yl)morpholine (29:71) was used. b

c

d

Other various aromatic enamines as well as the thienyl one easily participated in the reaction to give the corresponding P-hydroxy-P-trifluoromethyl ketone 3 in good to excellent yields (entries 2-7). However, the reaction of 4-nitropheyl substituted enamine 2e with la gave the only a 13% yield of the product 3e, probably due to the low solubility of 2e. Using toluene as the solvent improved the yield of 3e (entry 5). The reaction of the hemiacetal la with the mixture of


345

aliphatic enamines, such as 2i and 4-(3-methybut-l-en-2-yl)morpholine (29 : 71) gave 3h in 25% yield, and there is no detectable amount of the product, which reacts with the 4-(3-methybut-2-en-2-yl)morpholine, in the crude reaction mixture (entry 8). Trifluoroacetaldehyde hydrate (75 wt%) also reacted with the enamine 2a to produce 3a in 84% yield (entry 9).


Reaction with Various Imines The results of the reaction of trifluoroacetaldehyde ethyl hemiacetal l a with imines 4 derivedfromvarious methyl ketones are summarized in Table 2 (12).

Table 2. Reaction of Trifluoroacetaldehyde Ethyl Hemiacetal or Hydrate with Imines Derived from Various Methyl Ketones' 1

OH

Nc-Hex

F CÔX

+

3

hexane'

1

/ ^ R

1a: X = Et 1b :X = H

J,Î

4

OH Ο

F a C ^ ^ R

1

3

Entry

1

Imine

R

1 2 3 4 5 6 7 8 9 10 11

la la la la la la la la la la lb

4a 4b 4c 4d 4e 4f 4g 4h 4i 4j 4a

Ph 4-MeC H4 4-MeOC H4 4-ClC H4 4-N0 C H 4-EtOCOC H4 2-thienyl /-Pr c-Hex t-Bu Ph

l

6

6

6

2

6

4

6

Product

Yield (%f

3a 3b 3c 3d 3e 3i 3g 3h 3j 3k 3a

91 88 94 89 79 83 78 65 93 61 90

α

The reaction was carried out with trifluoroacetaldehyde ethyl hemiacetal la or hydrate lb (1 mmol) with imine 4(1 mmol) in hexane (4 ml) at reflux temperature. Yields of isolated pure products. b

Similar to the reaction of enamines 2, the reaction between the hemiacetal l a and various imines 4a-g with aromatic substituants including the thienyl group proceeded smoothly at reflux temperature to provide the corresponding β-


346

hydroxy-P-trifluoromethyl ketone 3a-e,g,i in good to excellent yields (entries 17). Of much significance is that the reaction of hemiacetal l a with aliphatic imines 4h-j carrying /-propyl, cyclohexyl, and /-butyl group, produced the products 3h-k in high yields (entries 8-10). For the imines with an /-propyl or chexyl group as R , although there are two kinds of tautomeric enamines in equilibrium, the reaction of the imines 4h,i with CF CHO proceeded with complete regioselectivity at the sterically less hindered α-position of the kinetic enamines to furnish the corresponding p-hydroxy-p-trifluoromethyl aliphatic ketones 3hj in good yields (Figure 1). No products 3h%j' derived from the more highly substituted enamines were observed in the reaction mixture based on the F NMR measurement. 1


3

19

Ν He-Hex

Nc-Hex

NHc-Hex

Figure 1.

Reaction of Various Polyfluoroalkylaldehyde Derivatives This methodology can be applied to the difluoroacetaldeh>de ethyl hemiacetal l c or pentafluoropropionaldehyde hydrate Id. Thus, the treatment of lc or Id with the enamine 3a or imine 4a gave the corresponding P-hydroxy-Pdifluoromethyl or pentafluoroethyl ketones 5 or 6 in good yields (Table 3, entries 1-4).



347

Table 3. Reaction of Polyfluoroalkylaldehyde Hemiacetal or Hydrate with Enamines or Imines Derived from Various Methyl Ketones"

OH

L

1c:Rf=CHF ,X=Et 1d: Rf = CF3CF2, X = H

Nc-Hex

J

2

2

4 OH hexane 1 h

Ο

5: Rf = C H F 6: R f = C F C F 2

3

Entry

1

2 or 4

R

1 2 3 4

lc lc Id Id

2a 4a 2a 4a

Ph Ph Ph Ph

1

Temp.

Product

Yield (%f

rt reflux rt reflux

5a 5a 6a 6a

65 67 78 70

a

2

The reaction was carried out with polyfluoroalkylaldehyde hemiacetal or hydrate 1 (1 mmol) with enamine 2 or imine 4 (1 mmol) in hexane (4 ml).


348

Reaction of Trifluoroacetaldehyde Ethyl Hemiacetal with Chiral Imines or Enamines


Reaction with Various Chiral Imines Next, we carried out the reaction between the trifluoroacetaldehyde ethyl hemiacetal l a and imines 7 carrying chiral auxiliaries (13). The results of the asymmetric reactions using chiral imines 7 under various conditions are summarized in Table 4. When the hemiacetal l a was allowed to react with an equimolar amount of the chiral imine 7a, derivedfromacetophenone and (R)-lphenylethylamine, in hexane at room temperature for 7 h, the aldol product 3a was obtained in 62% yield with a good enantiomer ratio (S:R = 80.1:19.9) (entry 1). The absolute configuration of the major isomer of 3a was assigned as S by comparison of the reported value of the optical rotation (14). Polarity of the solvent affects both the yields and enantiomer ratios of 3a. Less polar solvents, such as hexane and toluene (entries 1-2), are more suitable for the reaction than polar ones, such as THF, dichloromethane, and acetonitrile (entries 3-5). Among the examined chiral auxiliaries, the (i?)-l-(lnaphthyl)ethyl group was the most effective for the reaction to give 3a in 66% yield with the best enantioselectivity (entry 8). The reaction at 0 °C gave the product with a higher selectivity (entry 9). Lowering the reaction temperature to -15 °C did not have a significant effect on increasing the enantioselectivity (entry 10). The results of the reaction between the polyfluoroalkylaldehyde hemiacetal or hydrate 1 and various chiral imines 2 under the optimized conditions are summarized in Table 5. Aromatic, aliphatic, and heteroaromatic-substituted imines except for the 2-methylphenyl one participated nicely in the reaction with the trifluoroacetaldehyde ethyl hemiacetal l a or hydrate l b to afford the corresponding P-hydroxy-P-trifluoromethyl ketones 3 in good yields with good enantioselectivities (entries 1-6, 8-11). However, the reaction of the imine 2i containing the 2-methylphenyl group did not smoothly proceed with the only a 14% yield of the product 3f along with a low ee (entry 7). The reason for the decrease in both the yield and ee is unclear at present. Additionally, the present protocol is nicely applicable to the difluoroacetaldehyde ethyl hemiacetal lc or pentafluoropropionaldehyde hydrate Id, providing the good yields of the products 5a and 6a (entries 12 and 13). Compared with the trifluroacetladehyde ethyl hemiacetal, the use of difluoroacetaldehyde ethyl hemiacetal lc resulted in a reduction of the ee (entry 12). Furthermore, in the case of the trifluoromethylated or pentafluoroethylated products 3 or 6 with the aromatic group, the ee values of these products could be improved by a simple recrystallization method (15). However, this method was not effective for difluoromethylated ketone 4 due to its lower melting point compared to those of the trifluoromethylated ones.


349


Table 4. Reaction of Trifluoroacetaldehyde Ethyl Hemiacetal with Chiral Imines Derived from Acetophenone under Various Conditions"

OH

NR

+

+

F CTÔEt

X ^ p

3

1a

Ph^N

Λ

1) conditions 2)H*

2

n

solvent

7

π

? F

3

μ

n

H

9

C ^ ^ P h 3a

Ph^N Ph

7a

Entry" Imine Solvent

Conditions

Yield (%)* Isomer Ratio (5 : Rf

1 2 3 4 5 6 7 8 9 10

rt, 7h rt,7h rt,7h rt, 7 h it, 7 h rt, 7 h rt, 7 h rt, 7 h 0 °C, 7 d -15 °C, 7 d

62 64 8 61 56 73 92 66 57 48

7a 7a 7a 7a 7a 7b 7c 7d 7d 7d

hexane PhMe THF CH C1 MeCN hexane hexane hexane hexane hexane 2

2

80.1 :: 19.9 77.6: :22.4 73.3 ::26.5 71.3 ::28.7 71.9; : 28.1 20.6: :79.4 62.5 ::37.5 85.5: : 14.5 90.5 ;:9.5 89.3 :: 10.7

a

All the reaction was carried out with trifluoroacetaldehyde ethyl hemiacetal la (0.5 mmol) and chiral imine 7 (0.5 mmol) in hexane (2 ml). * Yields of isolated pure products, determined by HPLC analysis with CHIRALCEL OD (hexane:/-PrOH=95/5).


350

Table 5. Reaction of Polyfluoroalkylaldehyde Ethyl Hemiacetal or Hydrate with Various Chiral Imines

OH

NR

X R f O X

*

/ ^ P

1)0°C,7d 2)H+

2

1


1

1a: 1b: 1c: 1d:

7 R

Rf = C F , X = Et Rf = C F , X = H Rf = C H F , X = Et Rf=CF CF ,X = H 3

1

hexane

Rf

hexane

Rf' 3:Rf=CF 3: R f = C H F 5: 5: 6: R f = C F C F 3

2

3

2

3

R

2

3

1

7i: R = 2-MeC H 7j: R = 3-MeC H 7k: R = c-Hex 71: R = i-Pr 7m: R = f-Bu

1

7d: R = Ph 7e: R = 4-MeC H 7f: R = 4-CIC H 7g: R = 4-MeOC H 7h: R = 2-thienyl 4

4

1

6

4

1

Entry" 1

Imine Product Yield (%)* Er (S : Rf

Eé

Ee

1 2 3 4 5 6 7 g 9 10 11 12 13

7d 7d 7e 7f

81.0 78.2

92.8

78.8 75.2 72.0 80.6 13.8 81.2 86^ Iff 84^ 51.0 79.4

>99.9 >99.9 93.8 >99.9

e

?g 7h 7i 7j 7k 71 7m 7d 7d

3a 3a 3b 3c 3d 3e 3f 3g 3h 3i 3j 5a 6a

57 57 68 64 51 37 14 70 73 59 24 53 51

4

1

1

la lb la la la la la la la la la lc Id

4

6

1

1

6

6

1

1

6

2

90.5 :9.5 89.1 : 10.9 89.4: 10.6 87.6: 12.4 86.0: 14.0 90.3 :9.7 56.9:43.1 90.6:9.4 93 : / 88: 1 / 92 : 8 75.5 :24.5 89.7: 10.3 7

c4

-

-

95.6

a

All the reaction was carried out with 1 (0.5 mmol) and chiral imine 7 (0.5 mmol) in hexane (2 ml) at 0 °C for 7 d. * Yields of isolated pure products. Determined by HPLC analysis with CHIRALCEL OD (hexane:/-PrOH=95/5). After recrystallization. Toluene was used as a solvent. Determined by F NMR after the formation of Mosher's ester. 0

d

f

19


e

351

Reaction with Chiral Enamine The treatment of trifluoroacetaldehyde ethyl hemiacetal l a with the chiral enamine 8, prepared from acetophenone with (S)-2-(methoxymethyl)pyrrolidine (SMP) (16), in hexane under various reaction temperatures, unfortunately, gave 3a in 60-77% yields with very low selectivities, as shown in Table 6.

Table 6. Reaction of Trifluoroacetaldehyde Ethyl Hemiacetal with Chiral Enamine Derived from Acetophenone under Various Conditions'


1

~,, OH Γ X

F C OEt 3

ν

x

M ^ >

Ν

+

Λ

0

0

Μ

Ρ Η

1a

1) conditions 2) H

^ ~ QH Ο s η u

+

\ Θ

l ^ ^ F s C ^ ^ P h

8

3a

Entry

Conditions

Yield (%)

Isomer Ratio (S : R)

1 2 3

reflux, 1 h rt,lh 0 °C, 24 h

69 77 60

42.8: 57.2 50.1 :49.9 57.1 :42.9

b

c

a

All the reaction was carried out with trifluoroacetaldehyde ethyl hemiacetal la (0.5 mmol) and chiral enamine 8 (0.5 mmol) in hexane (2 ml). Yields of isolated pure products, determined by HPLC analysis with CHIRALCEL OD (hexane:/-PrOH=95/5). b

Proline-catalyzed Direct Aldol Reaction with Ketones Finally, a first novel catalytic in-situ generation of CF CHO from its hemiacetal as well as its successive direct asymmetric aldol reaction with some ketones was examined (17). The reaction of trifluoroacetaldehyde ethyl hemiacetal l a in the presence of a catalytic amount (30 mol%) of (I)-proline with acetone afforded P-hydroxy-P-trifluoromethyl ketone 31 with good enantioselectively. As summarized in Table 7, a survey of the reaction media revealed that various solvents could be used for this reaction. However, the employment of DMSO resulted in a significant loss of enantioselectivity (entry 1). The reaction in THF or hexane was sluggish and produced low yields of 31 (entries 2 and 7). The best enatioselectivity of 31 was obtained when benzene was used as the solvent but with a decreased yield (entry 6). Importantly, 3


352 acetone can be used as the solvent as well as a ketone donor with excellent yield and good enantioselectivity (entry 3). Both trifluoroacetaldehyde hydrate lb and pentafluoropropionaldehyde hydrate Id participated well in the (I)-proline-catalyzed direct aldol reaction to afford 31 or 6b in good yields with good enantioselectivities (entries 8 and 9).

Table 7. Direct Aldol Reaction of Trifluoroacetaldehyde Ethyl Hemiacetal with Acetone under Various Conditions Downloaded by EAST CAROLINA UNIV on November 3, 2016 | http://pubs.acs.org Publication Date: July 21, 2005 | doi: 10.1021/bk-2005-0911.ch019

0

OH ι RfÔX

* /,v

Ο η +

1a: Rf = C F , X = Et 1b: Rf = C F X = H 1d: Rf = C F C F , X = H 3

..

rt

4

"

8

h

31 : Rf = C F 6b : Rf = C F C F 3

2

2

Entry" 1

Solvent

Yield (%)*

Isomer Ratio (S : R) Eé

1 2 3 4 5 6 7 8 9

DMSO THF acetone** MeCN CH C1 benzene hexane acetone acetone

96 19 97 64 45 32 19 64 69

51.4:48.6 68.7:31.3 67.6 :32.4 70.7:29.2 73.9:26.1 75.8:24.2 73.0:27.0 68.9:31.1 72.0:28.0

la la la la la la la lb lc

Ο

3

3 l

3

OH

cat. (L)-proline solvent Rf

2

2

c

2.8 37.4 35.2 41.5 47.8 51.6 46.0 37.8 44.0

All the reaction was carried out with 1 (1 mmol) and 30 mol% of (Z)-proline in the mixed solvent of acetone (2 ml) and solvent (8 ml). * Determined by F NMR using benzotrifluoride as an internal standard. Determined by HPLC analysis with CHIRALCEL OD-H (hexane:/-PrOH=95/5) after p-chlorobenzoylation. Acetone, dehydrated (Kanto Chemical Co., Ltd.) was used. a

19

0

d

Surprisingly, in lieu of acetone, cyclopentanone or cyclohexanone reacted smoothly with the trifluoroacetaldehyde ethyl hemiacetal l a in the presence of 30 mol% of (I)-proline to give 57 to then quantitatively yield product 9 or 10


353

with high atftf-selectivities as well as excellent enantioselectivities (18) (Scheme 3).

F CÔEt 3

+

rS

solvent

1 1

(%

a

F (T

rt.48h

3

1

C)„

η = 1; 9 (quant ; syn/anti= 8/92, 97%ee) 3


a

η = 2; 10 (57% ; syn/anf/= 4/96, >98%ee) a

1 9

Measured by F NMR.

Scheme 3. In summary, we have determined that the novel stoichiometric in-situ generation of trifluoroacetaldehyde as well as its simultaneous asymmetric carbon-carbon bond formation reaction with enamines or imines, produced the corresponding P-hydroxy-P-trifluoromethyl ketones in good yields with high enantioselectivities. The major advantages of these processes are the use of only a stoichiometric amount of enamines or imines, good yields as well as high enantioselectivities, and no step required for the generation of trifluoroacetaldehyde. For the reaction of chiral imines, the recovery of the chiral auxiliary is quite easy. Furthermore, our new protocol can be nicely extended to the direct aldol reaction via the catalytic in-situ generation of trifluoroacetaldehyde from its hemiacetal using a catalytic amount of (X)-proline under extremely mild conditions.

Acknowledgment This work wasfinanciallysupported by a Grant-in-Aid for Encouragement of Young Scientists (B) (Grant No. 14750665) from the Ministry of Education, Culture, Sports, Science, the Gifu University, Nagoya Industrial Science Research Institute, the OGAWA Science and Technology Foundation, and the Central Glass Co., Ltd. We also thank the Central Glass Co., Ltd., for the gift of trifluoroacetaldehyde ethyl hemiacetal and hydrate. Finally, the author is grateful to Professor Dr. Masaki Matsui for his continued support and useful discussions.

References

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354


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Wouters, J.; Moureau, F.; Evrard, G.; Koenig, J.-J.; Jegham, S.; George, P.; Durant, F. Bioorg. Med. Chem. 1999, 7, 1683-1693. 3. For hemiacetal or hydrate, see: (a) Fernández, R.; Martín-Zamora, E.; Pareja, C.; Alcarazo, M.; Martín, J.; Lassaletta, J. M . Synlett 2001, 1158-1160. (b) Gong, Y.; Kato, K.; Kimoto, H. J. Heterocyclic Chem. 2001, 38, 25-28. (c) Shirai, K.; Onomura, O.; Maki, T.; Matsumura, Y. Tetrahedron Lett. 2000, 41, 5873-5876. (d) Kuwano, R.; Miyazaki, H.; Ito, Y. J. Organomet. Chem. 2000, 603, 18-29. (e) Gong, Y.; Kato, K.; Kimoto, H. Bull. Chem. Soc. Jpn. 2000, 73, 249-250. (f) Loh, T. -P.; Li, X. -R. Tetrahedron 1999, 55, 56115622. (g) Sakumo, K.; Kuki, N.; Kuno, T.; Takagi, T.; Koyama, M.; Ando, Α.; Kumadaki, I. J. Fluorine Chem. 1999, 93, 165-170. (h) Gong, Y. F.; Kato, K.; Kimoto, H. Synlett 1999, 1403-1404. (i) Loh, T. -P.; Xu, K. C.; Ho, D. S. C.; Sim, Κ. Y. Synlett 1998, 369-370. (j) Omote, M.; Ando, Α.; Takagi, T.; Koyama, M.; Kumadaki, I. Tetrahedron 1996, 52, 13961-13970. (k) Ishihara, T.; Hayashi, H.; Yamanaka, H. Tetrahedron Lett. 1993, 34, 5777-5780. (l) Kubota, T.; Iijima, M.; Tanaka, T. Tetrahedron Lett. 1992, 33, 1351-1354. (m) Guy, Α.; Lobgeois, M . J. Fluorine Chem. 1986, 32, 361-366. For trifluoroacetaldehyde other derivatives, see: (n) Matsutani, H.; Poras, H.; Kusumoto, T.; Hiyama, T. Chem. Commun. 1998, 1259-1260. (ο) Matsutani, Η.; Poras, Η.; Kusumoto, T.; Hiyama, T. Synlett 1998, 13531354. (p) Matsutani, Η.; Kusumoto, T.; Hiyama, T. Chem. Lett. 1999, 529530. (q) Xu, Y.; Dolbier, Jr., W. R. Tetrahedron Lett. 1998, 39, 9151-9154. 4. For the reaction with boron enolates, see: (a) Iseki, K.; Kobayashi, Y. Chem. Pharm.Bull.1996, 44, 2003-2008. (b) Iseki, K.; Oishi, S.; Kobayashi, Y . Tetrahedron 1996, 52, 71-84. (c) Makino, Y.; Iseki, K. Oishi, S.; Hirano, T.; Kobayashi, Y. Tetrahedron Lett. 1995, 36, 6527-6530. For with a lithium enolate, see: (d) Qian, C.-P.; Liu, Y. - Z . ; Tomooka, K.; Nakai, T. Org. Synth. 1999, 76, 151-158. (e) Qian, C. P.; Nakai, T.; Dixon, D. Α.; Smart, Β. E. J. Am. Chem. Soc. 1990, 112, 4602-4604. (f) Patel, D. V.; Rielley-Gauvin, K.; Ryono, D. E; Free, C. Α.; Smith, S. Α.; Petrillo, E. W. J. Med. Chem. 1993, 36, 2431-2441. (g) Patel, D. V.; Rielley-Gauvin, K.; Ryono, D. E. Tetrahedron Lett. 1988, 29, 4665-4668. (h) Seebach, D.; Juaristi, E.; Miller, D. D.; Schickli, C.; Weber, T. Helv. Chem. Acta 1987, 70, 237-261. (i) Yamazaki, T.; Takita, K.; Ishikawa, N . Nippon Kagaku Kaishi 1985, 2131-2139. (j) Tius, Μ. Α.; Savariar, S. Tetrahedron Lett. 1985, 26, 3635-3638. For with a zinc enolate, see: (k) Watanabe, S.; Sakai, Y.; Kitazume, T.; Yamazaki, T. J. Fluorine Chem. 1994, 68, 59-61. For with a nickel enolate, see: (l) Soloshonok, V. Α.; Kukhar, V. P.; Galushko, S. V.; Svistunova, N . Y.; Avilov, D. V.; Kuz'mina, N . A,; Raevski, N. I.; Struchkov, Y. T.; Pysarevsky, A. P.; Belokon, Y. N . J. Chem.Soc.,Perkin Trans. 1 1993, 3143-3155.



355 5. (a) Mikami, K.; Yajima, T.; Takasaki, T.; Matsukawa, S.; Terada, M . ; Uchimaru, T.; Maruta, M . Tetrahedron 1996, 52, 85-98. (b) Ishii, Α.; Kojima, J.; Mikami, K. Org. Lett. 1999, 1, 2013-2016. (c) Ishii, K.; Mikami, K. J. Fluorine Chem. 1999, 97, 51-55. 6. (a) Hayashi, E.; Takahashi, Y.; Itoh, H.; Yoneda, N . Bull. Chem. Soc. Jpn. 1994, 67, 3040-3043. (b) Ogawa, K.; Nagai, T.; Nonomura, M.; Takagi, T.; Koyama, M . ; Ando, Α.; Miki, T.; Kumadaki, I. Chem. Pharm. Bull. 1991, 39, 1707-1712. (c) Pautrat, R.; Marteau, J.; Cheritat, R. Bull. Soc. Chim. Fr. 1968, 1182-1186. (d) Mikami, K. Yajima, T.; Siree, N.; Terada, M.; Suzuki, Y.; Kobayashi, I. Synlett 1996, 837-838. 7. (a) Shermolovich, Y. G.; Yemets, S. V. J. Fluorine Chem. 2000, 101, 111111. (b) Ishii, Α.; Soloshonok, Α. V.; Mikami, K. J. Org. Chem. 2000, 65, 1597-1599. 8. Reddy, M . V. R.; Rudd, M . T.; Ramachandran, P. V. J. Org. Chem. 2002, 67, 5382-5385. 9. (a) Braid, M.; Iserson, H.; Lawlore, F. E. J. Am. Chem. Soc. 1954, 76, 4027. (b) Henne, A. L.; Pelley, R. L.; Alm, R. M . J. Am. Chem. Soc. 1950, 72, 3370-3371. (c) Shechter, H.; Conrad, F. J. Am. Chem. Soc. 1950, 72, 33713373. 10. Ishii, Α.; Terada, Y. J. Syn. Org. Chem. Jpn. 1999, 57, 898-899. 11. For a preliminary communication, see: (a) Funabiki, K.; Nojiri, M.; Matsui, M.; Shibata, K. Chem. Commum. 1998, 2051-2052. For a fullpaper, (b) Funabiki, K.; Matsunaga, K.; Nojiri, Hashimoto, W.; Yamamoto, H.; Shibata, Κ.; M.; Matsui, M . J. Org. Chem. 2003, 68, 2853-2860. 12. For a preliminary communication, see: (a) Funabiki, K.; Matsunaga, K.; Matsui, M.; Shibata, K. Synlett 1999, 1477-1479. For a full paper, ref. 11b. 13. Shibata, K.; Matsui, M . ; Funabiki, K. Jpn. Kokai Tokkyo Koho, JP 2001226308 (2001). Funabiki, K.; Hashimoto, W.; Matsui, M . Chem. Commun. in press. 14. Lin, J.-T.; Yamazaki, T.; Kitazume, T. J. Org. Chem. 1987, 52, 3211-3217. 15. Ishii, Α.; Kanai, M.; Higashiyama, K.; Mikami, K. Chirality 2002, 14, 709712. 16. Enders, D.; Klatt, M . Synthesis 1996, 1403-1418. 17. Funabiki, K.; Yamamoto, H.; Nagamori, M.; Matsui, M.; Jpn. Kokai Tokkyo Koho, submitted (application No. 2003—403268) (2003). 18. Very recently, Saito and Yamamoto have published a similar result of cyclopentanone using other organocatalyst, see: Torii, H.; Nakadai, M.; Ishihara, K.; Saito, S.; Yamamoto, H. Angew. Chem., Int. Ed. 2004, 43, 1983-1986.


Fluorine-Containing Synthons

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