Chirality transfer from 4-methylcyclohexylidenemethyl(phenyl)iodonium tetrafluoroborate to 4-methylcycloheptanone during solvolysis: Evidence against a primary vinylic cation as intermediate [6]

Journal of the American Chemical Society

Volumn 122, Issue 36, 2000, Pages 8787-8788

  Fujita, Morifumi ^a   Sakanishi, Yuichi ^a   Okuyama, Tadashi ^a  

^a UNIVERSITY OF HYOGO   (Japan)

Author keywords

[No Author keywords available]

Indexed keywords

4 METHYLCYCLOHEPTANONE; 4 METHYLCYCLOHEXYLIDENEMETHYL(PHENYL)IODONIUM TETRAFLUOROBORATE; UNCLASSIFIED DRUG; VINYL DERIVATIVE;

CHEMICAL STRUCTURE; CHIRALITY; ENANTIOMER; LETTER; OPTICAL ROTATION; PHOTOLYSIS; STEREOCHEMISTRY;

EID: 0034644440     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja001509x     Document Type: Letter

References (32)

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15. 3) δ 164.6, 134.5, 132.3, 132.2, 110.4, 91.8, 36.5, 36.1, 35.7, 35.1, 31.4, 21.0.
16. 14 this is the first example of iodonium salts carrying a chiral and reactive vinyl moiety.
17. Ochiai, M.; Kitagawa, Y.; Takayama, N.; Takaoka, Y.; Shiro, M. J. Am. Chem. Soc. 1999, 121, 9233-9234.
18. (a) Perkin, W. H.; Pope, W. J. J. Chem. Soc. 1911, 99, 1510-1529.
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21. 18 The vinyl bromide obtained was 66% excess of the S form, determined using the chiral GC-column. This indicates that the substitution proceeds with 92% [= 100 × (66/78 + 1)/2] inversion. A sample of 1 obtained by crystallization of the crude mixture was also converted under the same conditions to the vinyl bromide which was of 58% ee. This means that the ee of the sample of 1 was 69% [= 58/(2 × 0.92-1)]. If the conversion of the vinylsilane to 1 would proceed with partial loss of ee, the ee of the crystallized 1 should be lower than 69%. On the contrary, the 69% ee of product 2 obtained in the solvolysis experiments implies that the ee of the substrate 1 is not lower than 69% unless enantiomeric enrichment occurs during the reaction. These results are also consistent with complete retention of configuration in the formation of vinyliodonium salts from the corresponding vinylsilanes.
22. (a) Ochiai, M.; Oshima, K.; Masaki, Y. J. Am. Chem. Soc. 1991, 113, 7059-7061.
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24. (c) Okuyama, T.; Takino, T.; Sato, K.; Ochiai, M. J. Am. Chem. Soc. 1998, 120, 2275-2282.
25. A sample of 1 or the racemic salt (1-5 mg) was dissolved in 1-5 mL of the solvent and kept at 60 °C under stirring for a specified reaction time. The products were extracted with ether and washed with water. The yields of the products from the racemic substrate were determined by gas chromatography with tetradecane as an internal standard, while the ee of the products from 1 were determined using the chiral GC-column.
26. 4 byproduct.
27. An authentic sample of optically active 2 was prepared from commercially available (R)-3-methylcyclohexanone. It was reacted with ethyldiazoacetate to give a diastereomeric mixture of (4R)-4-methyl- and (3R)-3-methyl-2-ethoxycarbonylcycloheptanones, which was subjected to hydrolysis and decarboxylation to afford a mixture of (R)-4-methyl- and (R)-3-methylcycloheptanones. The former isomer coincided with the major enantiomer of product 2 upon co-injection in the chiral GC-column.
28. Similar reactions were characterized in the presence of a strong base. (a) Ochiai, M.; Takaoka, Y.; Nagao, Y. J. Am. Chem. Soc. 1988, 110, 6565-6566. (b) Ochiai, M.; Kunishima, M.; Tani, S.; Nagao, Y. J. Am. Chem. Soc. 1991, 113, 3135-3142. (c) Ochiai, M.; Sueda, T.; Uemura, K.; Masaki, Y. J. Org. Chem. 1995, 60, 2624-2626.
29. Similar reactions were characterized in the presence of a strong base. (a) Ochiai, M.; Takaoka, Y.; Nagao, Y. J. Am. Chem. Soc. 1988, 110, 6565- 6566. (b) Ochiai, M.; Kunishima, M.; Tani, S.; Nagao, Y. J. Am. Chem. Soc. 1991, 113, 3135-3142. (c) Ochiai, M.; Sueda, T.; Uemura, K.; Masaki, Y. J. Org. Chem. 1995, 60, 2624-2626.
30. Similar reactions were characterized in the presence of a strong base. (a) Ochiai, M.; Takaoka, Y.; Nagao, Y. J. Am. Chem. Soc. 1988, 110, 6565- 6566. (b) Ochiai, M.; Kunishima, M.; Tani, S.; Nagao, Y. J. Am. Chem. Soc. 1991, 113, 3135-3142. (c) Ochiai, M.; Sueda, T.; Uemura, K.; Masaki, Y. J. Org. Chem. 1995, 60, 2624-2626.
31. Yamataka, H. Personal communication, February, 2000.
32. N2-type reaction with retention (via perpendicular attack) is a viable alternative.