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Organic Synteses vol 69 - Paquette L.A.

Paquette L.A., Boecman R.K. Organic Synteses vol 69 - John Wiley & Sons, 1990. - 174 p.
ISBN 0-471-54560-0
Download (direct link): organicsynthesesvol691990.pdf
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Scheme 1
Roflamycoin
85
has an array of 1,3-secondary hydroxyl groups, assumed to bear an all-syn relationship to each other, for which a synthetic strategy has been devised.12-14 Thus, a reiterative 2-step protocol involving epoxide opening with a H.O. vinylcyanocuprate, followed by stereoselective homoallylic alcohol epoxidation, reforms the functionality (i.e., an epoxide) from which it was originally derived (Scheme 2).
Scheme 2
Y7’C'O'^'Ph O H
1. Department of Chemistry, University of California, Santa Barbara, CA 93106.
2. Watson, S. C.; Eastham, J. F. J. Organomet. Chem. 1967, 9,165.
3. Still, W. C.; Kahn, M.; Mitra, A. J. Org. Chem. 1978, 43, 2923.
4. Chittenden, G. J. F. Carbohydr. Res. 1980, 84, 350.
5. Takano, S.; Goto, E.; Hirama, M.; Ogasawara, K. Heterocycles 1981, 16, 381.
6. Golding, B. T.; loannou, P. V. Synthesis 1977, 423.
7. Anisuzzaman, A. K. M.; Owen, L. N. J. Chem. Soc. (C) 1967,1021.
8. Lipshutz, B. H.; Kozlowski, J. A.; Parker, D. A.; Nguyen, S. L.; McCarthy, K. E. J. Organomet. Chem. 1985, 285, 437.
9. Lipshutz, B. H.; Koemer, M.; Parker, D. A. Tetrahedron Lett. 1987, 28, 945.
10. For reviews, see: (a) Lipshutz, B. H. Synthesis 1987, 325; (b) Lipshutz, B. H.; Wilhelm, R. S.; Kozlowski, J. A. Tetrahedron 1984, 40, 5005.
11. Posner, G. H. Org. React. 1975, 22, 253.
12. Lipshutz, B. H.; Kozlowski, J. A. J. Org. Chem. 1984, 49,1147.
(2-Thienyl)Cu(CN)U2
1)
2} epoxidation 3) repeat ol 1) and 2)
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13. Lipshutz, В. H.; Kotsuki, H.; Lew, W. Tetrahedron Lett. 1986, 27, 4825.
14. Lipshutz, В. H.; Moretti, R.; Crow, R. Tetrahedron Lett. 1989, 30, 15.
Appendix
Chemical Abstracts Nomenclature (Collective Index Number); (Registry Number)
1-Benzyloxy-4-penten-2-ol: 4-Penten-2-ol, 1-{phenylmethoxy)- (9); (58931-16-11) Thiophene (8,9); (110-02-1)
Butyllithium: Lithium, butyl- (8,9); (109-72-8)
Copper(l) cyanide: Copper cyanide (8,9); (544-92-3)
Vinyllithium: Lithium, vinyl- (8); Lithium, ethenyl- (9); (917-57-7)
Benzyl 2,3-epoxypropyl ether: Propane, 1-(benzyloxy)-2,3-epoxy- (8); Oxirane, [(phenylmethoxy)methyl]- (9); (2930-05-4)
Glycidol: 1-Propanol, 2,3-epoxy- (8); Oxiranemethanol (9); (556-52-5)
Benzyl bromide: Toluene, a-bromo- (8); Benzene, (bromomethyl)- (9); (100-39-0) Tetrabutylammonium iodide (8); 1-Butanaminium, N,N,N-tributyl-, iodide (9); (311-28-4)
(S)-Benzyl 2,3-epoxypropyl ether: Propane, 1-(benzyloxy)-2,3-epoxy-, (S)- (8,9); (14618-80-5)
D-Mannitol (8,9); (69-65-8)
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Table
Reactions of Various Substrates with (Vinyl)(2-thienyl)Cu(CN)Li2 Substrate of cup rate Conditions Product Yield(0/
1.20
1.50
THF/Et20 room temp. 4 hr
THF, 31° 18 hr
71°
67"
1.10
THF/EtjO 1.1 eq. BF3 -78°, 1 hr
98“
1.25
THF/Et20 0°, 1 hr
90“
isolated yield of chromatographicaiiy pure material. bBy quantitative GC analysis.
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THE CONVERSION OF ESTERS TO ALLYLSILANES: TRIMETHYL(2-METHYLENE-4-PHENYL-3-BUTENYL)SILANE (Silane, trimethyl (2-methylene-4-phenyl-3-butenyl)-)
O
CH2
C6H5^'^^^OC2H5 + (CH3)3SiCH2MgCI
'CH2Si(CH3)3
Submitted by William H. Bunnelle and B. A. Narayanan.1 Checked by Jürgen Fischer and Ekkehard Winterfeldt.
1. Procedure
A 1-L, three-necked, round-bottomed flask with mechanical stirrer and vacuum outlet (Note 1) is charged with powdered cerium(lll) chloride (CeCl3-7H20, 52.92 g,
0.142 mol) (Note 2). The flask is immersed to the necks in an oil bath and evacuated to 0.2 mm. The solid is agitated by stirring as the flask is heated to 150°C for 2 hr. After the flask is cooled to room temperature, it is vented to the atmosphere, and quickly purged with a stream of dry nitrogen for 2 min. At this stage, the flask is fitted with a low-temperature thermometer and a graduated 250-mL addition funnel containing 300 mL of dry tetrahydrofuran (THF) (Note 3), and capped with a rubber septum. Connection to a dry nitrogen line with a pressure relief bubbler is made via a needle through the septum. Tetrahydrofuran is run into the flask with good stirring, so that an even suspension results (Note 4). The white suspension is stirred at room temperature for 2 hr. Meanwhile, the addition funnel is charged with trimethylsilylmethylmagnesium chloride (Me3SiCH2MgCI, 1 M solution in ethyl ether, 142 mL, 0.142 mol) (Notes 5 and 6), transferred via stainless steel cannula. The contents of the flask are cooled to -65°C with a dry ice-2-propanol bath, and the
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Grignard solution is added dropwise over a period of 40-50 min, so that the temperature of the reaction mixture remains below -60°C. The addition funnel is removed from the setup, with the septum/nitrogen inlet connected directly to the flask. After the cold mixture is stirred for 15 min more, ethyl cinnamate (10.32 g, 0.0586 mol) (Note 7) is added via syringe over a 2-3 min period. Stirring is continued as the flask is allowed to warm slowly to room temperature (Note 8). The off-white to beige reaction mixture is cooled to <5°C (ice-water bath) and quenched by the portion-wise addition of chilled 1 M hydrochloric acid (200 mL), so that the internal temperature remains below 20°C (Note 9). The layers are separated, and the aqueous phase is extracted twice with ethyl ether (100 mL each). The combined organic layers are washed with saturated sodium bicarbonate solution (Note 10), dried over sodium sulfate, and the solvents are removed at a rotary evaporator (25°C/60 mm). The residual oil is transferred to a 100-mL, round-bottomed flask and distilled bulb-to-bulb (Note 11). The product (9.69-9.85 g, 76.5-78%) (Note 12) is collected at an air bath temperature of 110-112°C, 0.20 mm.
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