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11
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84919127899
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Wehmeyer, R.M.; Rieke, R.D. in press.
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12
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84919127898
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3P (18.6 mmol) in freshly distilled THF (10 mL) at ambient temperature for 1 h. The reaction mixture was stirred at 0 °C for 0.5 h and was then cooled to −45 °C. GC internal standard (e.g. n-undecane) and 5-bromo-1,2-epoxypentane (2.2 mmol) in 10 mL of THF was rapidly added to the activated copper at −45 °C. After stirring at −45 °C for 5 min, the reaction mixture was allowed to warm to −23 °C. The reaction mixture was stirred at −23 °C for additional 3 h and was gradually warmed to room temperature. Aliquots [[Truncated]]
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13
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84919127897
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Treatment of epoxide 1 with an excess magnesium in the presence of 0.5 molar equiv of CuI yielded a 4 : 1 mixture of 4 : 3 in 34% yield, see
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15
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84919127896
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Cyclization of haloepoxide 1 with lithium and CuI in THF gave cyclohexanol (4) as a sole product in 25% yield, see:
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17
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84919127895
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2O-pentane (1:1) afforded a 4.4 : 1 mixture of 4 : 3 in 59% yield
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19
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84919127894
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In contrast, Babler and Bauta reported that similar treatment of haloepoxide 1 with s-BuLi in the presence of CuI produced a 16 : 1 mixture of 3 : 4, see ref. 2b.
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20
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84919127893
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2O-pentane (1:1) gave a 10 : 1 mixture of 3 : 4
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22
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84919127892
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2O-hexane (1:1) yielded a 24 : 1 mixture of 3 : 4
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24
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84919127891
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Treatment of o-bromophenyl 2,3-epoxypropyl ether with n-BuLi in THF-hexane (4:1) afforded only 5-membered ring product
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27
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84919127890
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Baldwin's rules do not consider the substituent effects. Upon substitution at reactive sites of a molecule, regiochemistry is often changed to sterically minimize the nonbonding interactions involved in the transition state.
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28
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84919127889
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2S afforded a <1 : 100 mixture of 9 : 10 in 30% yield
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30
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84919127888
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The relationship between donating ability of phosphine and reactivity of generated organocopper species has been found by Wehmeyer
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32
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84919127887
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Wehmeyer, R.M.; Rieke, R.D. in press.
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33
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84919127886
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4 reduction of cyclobutyl methyl ketone. The spectroscopic data of this synthesized alcohol are identical to those obtained from the cyclized product.
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34
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84919127885
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The minor product was tentatively assigned as cis-2-methylcyclopentanol (16) by comparison of our proton NMR spectra with literature data
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36
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84919127884
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Baldwin, in his “rules for ring closure”, described that “the rules for opening three-membered rings to form cyclic structures, seem to lie between those for tetrahedral and trigonal systems, generally preferring Exo-modes”
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38
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84919127883
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2S
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40
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84919127882
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In contrast, Erdik reported that only cyclobutanol formation was observed in the cyclization of epoxide 17 with Mg or Li in the presence of CuI in 7–8% yield
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42
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84919127881
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Cooke, Jr. and Houpis reported that only 6-membered ring formation was observed with no evidence of any 7-membered ring formation
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44
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84919127880
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Trapping the cyclized alkoxides with acid chlorides to form a higher boiling point derivative will prevent the evaporation of volatile cycloproducts and facilitate the isolation. For example, cyclopropanemethyl benzoate was isolated in 77% yield, see ref. 3e. In a trapping procedure, benzoyl chloride (1 eq) was added at −35 °C. The reaction mixture was stirred at −35 °C for 30 min and was then warmed to room temperature. The reasonably pure product (〉99%) can be obtained by flash-column chromatography twice on silica gel. The highly pure product can be obtained by preparative thin-layer chromatography.
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