[594-19-4]  · C4H9Li  · t-Butyllithium  · (MW 64.06)

(strong base capable of lithiating weak acids;1 useful for heteroatom-faciliated lithiations;2-4 reagent of choice for lithium-halogen exchange;5 can add to p-bonds1,6)

Physical Data: colorless solid; decomposes above 140 °C with loss of LiH; sublimes at 70 °C/0.1 mmHg. X-ray structures of the solvent-free tetramer and the ether-solvated dimer7a and 13C NMR studies in hydrocarbon8a and ethereal solutions7b have been reported.

Solubility: sol hydrocarbon solvents, diethyl ether, and THF but should be used at low temperature; half-lives in various solvents have been reported;9 reacts violently with H2O and other protic solvents.

Form Supplied in: commercially available as an approximately 1.7 M solution in pentane or heptane. Tetrameric in hydrocarbons,8 dimeric in diethyl ether,7 monomeric in THF10a although earlier reported as dimeric.1,10b In combination with tertiary polyamines such as N,N,N,N-Tetramethylethylenediamine (TMEDA), 1,4-Diazabicyclo[2.2.2]octane (DABCO), or N,N,N,N,N-Pentamethyldiethylenetriamine (PMDTA), reactivity is often increased.1,11

Analysis of Reagent Purity: since the concentrations of commercial solutions vary appreciably, especially after the original seal is broken, it is necessary to standardize solutions of the reagent prior to use. The classical Gilman double titration method is described in detail by Wakefield.1b A particularly convenient method for routine analyses involves titration of the reagent with s-butyl alcohol using 1,10-phenanthroline or 2,2-biquinoline as indicator.13 A variety of other methods have been described.14

Preparative Method: the reaction of t-butyl chloride with 1-2% Na-Li alloy in dry pentane requires particular attention to detail to achieve a reasonable yield of the reagent. Detailed procedures should be consulted.1b,12

Handling, Storage, and Precautions: solutions of the reagent are pyrophoric and the reagent may ignite spontaneously upon exposure to air, producing a purple flame. It is prudent to conduct all operations involving t-BuLi behind a shield. In case of fire, a dry-powder extinguisher should be used: in no case should an extinguisher containing water or halogenated hydrocarbons be used to fight an alkyllithium fire. Bottles and reaction flasks containing the reagent should be flushed with N2 or preferably Ar and kept tightly sealed to preclude contact with oxygen or moisture. The reagent may be cautiously transferred under an inert gas atmosphere using standard syringe/cannula techniques.1b Most reactions of t-butyllithium are exothermic and for this reason are usually carried out at temperatures well below ambient. For detailed handling techniques see Wakefield.1b


t-Butyllithium is less frequently used for proton abstraction than is n-Butyllithium or s-Butyllithium. However, as it is more reactive and less nucleophilic than its isomers, t-BuLi may be the reagent of choice for the lithiation of relatively weak acids (eq 1). The addition of 1 equiv of a tertiary polyamine increases the metalating ability of the reagent.1,11 Simple hydrocarbons, which are used as solvents, are generally inert to lithiation by t-BuLi. Although ethers and amines are often used as solvents in low temperature reactions involving t-BuLi, ethers,15 THF,16 and TMEDA17 are readily lithiated by the reagent. Indeed, treatment of THF with t-BuLi has been reported to afford ethylene and the lithium enolate of acetaldehyde at temperatures as low as -78 °C.16a

Monodeprotonation of terminal alkynes is conveniently accomplished with n-BuLi (see Propynyllithium); the use of excess t-BuLi in hexane may lead to polylithiation.18 For example, treatment of 1-butyne with 3 equiv of t-BuLi in hexane affords a mixture of allene and alkyne upon quench with an electrophile (eq 2).19

Highly regioselective proton abstractions may result when substrates containing such heteroatoms as oxygen, nitrogen, sulfur, and the like are treated with an organolithium. Several reviews of the topic2-4,6,20 and a collection of detailed experimental procedures21 are available. Two categories of heteroatom-facilitated lithiations are recognized: a-lithiation, involving removal of a proton from the carbon bearing the heteroatom, and b- (or ortho-) lithiation, involving abstraction of a proton from the b-position.2,4 Lithiation of acyclic22 (eq 3),22a cyclic (eq 4),23 and conjugated enol ethers (eq 5)24 using t-BuLi provides a simple route to readily functionalized a-lithio vinyl ethers (see 1-Ethoxyvinyllithium). Vinyl sulfides behave analogously25 and sulfur appears to be a stronger a-director than is oxygen (eq 6).26 Alkyl phenyl thioethers are a-lithiated by t-BuLi in the presence of Hexamethylphosphoric Triamide (eq 7).27 Furans and thiophenes are readily a-lithiated by t-BuLi, but use of the less reactive n-BuLi is more convenient.1,2,21 At temperatures below -100 °C, t-BuLi in THF regioselectively deprotonates enamines derived from b-acyl aldehydes in preference to 1,2- or 1,4-addition28 (eq 8).28a

Heteroatom-directed ortho lithiations of aromatic compounds are most often accomplished with n- or s-BuLi, either alone or in combination with TMEDA.4 Some benefit derives from the use of the bulkier and more basic t-BuLi for ortho lithiation of substrates bearing substituents susceptible to nucleophilic attack (eq 9)29 or resistant to deprotonation by less reactive bases (eq 10)9,30 The key step in a highly stereoselective asymmetric synthesis of chiral ferrocenes involves ortho lithiation of a ferrocenyl acetal at -78 °C using t-BuLi in THF (eq 11).31

Lithium-Halogen Exchange.

t-Butyllithium is often the reagent of choice for the preparation of an organolithium by lithium-halogen exchange. The reversible metathesis (eq 12), most readily accomplished at low temperature with bromides and iodides, leads to an equilibrium mixture favoring the more stable organolithium.1,32 The benefits of using t-BuLi (rather than n- or s-BuLi) for the preparation of organolithiums by lithium-halogen exchange derives from two considerations: (1) the interchange equilibrium is favorable when an aryl, vinyl, cyclopentyl, or primary-alkyl halide is treated with a tertiary organolithium,33 and (2) the exchange may be rendered operationally irreversible by employing 2 equiv of t-BuLi since 1 equiv of the reagent rapidly consumes the t-butyl halide generated in the reaction to give isobutane, isobutene, and lithium halide (eq 13).34

Aryl halides readily undergo lithium-halogen exchange with alkyllithiums in ethereal solvents at temperatures at or below -78 °C and the less expensive n-BuLi is often used for this purpose.1,32 However, the presence of the n-butyl halide product can cause complications when the aryllithium is warmed since a coupling reaction may ensue1,32 (for example, the reaction of Phenyllithium with n-butyl iodide in THF at -78 °C has a half-life of ~30 min). This potential problem is avoided when 2 equiv of t-BuLi are used for the generation of aryllithiums.

Vinyllithiums are readily prepared with retention of configuration from the corresponding vinyl bromides or iodides in a stereoselective exchange with 2 molar equiv of t-BuLi, provided that the reaction is conducted at temperatures below -110 °C.35 The reactions are conducted most conveniently in the Trapp solvent,36 a 4:4:1 mixture of THF, diethyl ether, and pentane (or hexane), by slow addition of 2 equiv of t-BuLi in pentane to a solution of the halide which is held at -110 to -120 °C. The preparation of (E)-1-hexenyllithium and its conversion to (E)-1-phenylthio-1-hexene is illustrative (eq 14)35a of the method, and detailed experimental procedures are available.37 The stereoselective lithium-halogen exchange of vinyl halides is the key step in a highly diastereoselective metalla-Claisen rearrangement (eq 15)38 and a-keto dianions may be prepared from the lithium enolates of a-bromo ketones by the exchange reaction with excess t-BuLi (eq 16).39

Cyclopropyllithiums (see Cyclopropyllithium) are, in general, easily prepared from the corresponding bromides or iodides with retention of configuration by low-temperature lithium-halogen exchange using either n-BuLi or t-BuLi.1,32 The more reactive t-BuLi was found to be superior for the generation of (1-ethoxycyclopropyl)lithium, a reagent useful for the preparation of cyclobutanones (eq 17).40

The early literature suggests that metal-halogen exchange between primary alkyl halides and alkyllithiums is not, in general, a preparatively useful reaction due to unfavorable equilibria (eq 12) and competition from coupling and elimination reactions.1,32 However, more recent mechanistic studies of the exchange reaction41,42 have revealed that virtually all of the difficulties historically associated with use of this method for the preparation of simple alkyllithiums can be overcome by the use of t-BuLi and judicious choice of experimental conditions.5 Primary alkyllithiums are conveniently prepared at -78 °C (the exchange has been conducted at temperatures as low as -131 °C)5a by addition of 2.1-2.2 equiv of t-BuLi in pentane to a solution of primary alkyl iodide in pentane-diethyl ether (3:2 by vol).5 Under these conditions (eq 18) the exchange is exceedingly rapid, the yield of alkyllithium is excellent,5 and the only byproduct is a small quantity of easily removed hydrocarbon derived from formal reduction of the iodide via proton abstraction from the cogenerated t-BuI.43 The alkyllithium may be used at low temperature but residual t-BuLi remaining in solution may complicate product isolation following addition of an electrophile to the cold reaction mixture, particularly if an excess of t-BuLi was employed. Any residual t-BuLi is easily removed by simply allowing solutions containing the primary alkyllithium and t-BuLi to warm to room temperature: the t-BuLi is rapidly consumed by proton abstraction from diethyl ether, leaving clean solutions of the less reactive primary alkyllithium.5 The success of this route to primary alkyllithiums depends critically on the appropriate choice of both halide and solvent.5 Alkyl iodides rather than alkyl bromides or chlorides must be used in the exchange: under the conditions of the reaction (eq 18), lithium-iodine exchange most probably involves rapid attack of t-BuLi on the iodine atom of the halide,42,44 while lithium-bromine exchange occurs predominantly by a single electron transfer (SET) mechanism.42 Alkyl chlorides are essentially inert to the action of t-BuLi under the conditions indicated in eq 18.42 Moreover, it is advisable to run the reaction in a solvent system that contains diethyl or a similar ether; the use of THF or other strongly coordinating Lewis bases such as TMEDA should be avoided as elimination and coupling reactions may compete with exchange in these solvents.5a

Low-temperature lithium-iodine exchange with t-BuLi has been used to prepare 5-hexenyllithiums from 6-iodo-1-hexenes.43 When warmed, these alkenic alkyllithiums undergo highly stereoselective and totally regiospecific 5-exo cyclization via a cyclohexane chair-like transition state45 to afford high yields of (cyclopentylmethyl)lithiums that may be functionalized by reaction with an electrophile46 (eq 19).46b Such isomerizations have also been conducted in a tandem fashion to give polycyclic products47 (eq 20).47a Alkynic alkyllithiums, which are prepared by lithium-iodine exchange with t-BuLi, cyclize in a stereoselectively syn fashion to four-, five-, and six-membered carbocyclic rings bearing an exocyclic lithiomethylene moiety48 (eq 21).48a Related chemistry initiated by lithium-selenium exchange with t-BuLi has also been reported.49

Reaction of 2 equiv of t-BuLi with a,o-diiodoalkanes at -23 °C affords nearly quantitative yields of three- through five-membered carbocyclic rings via cyclization of an intermediate a-lithio-o-iodoalkane (eq 22).50 When 4 equiv of t-BuLi are used at -78 °C, a,o-dilithioalkanes such as 1,4-Dilithiobutane, 1,5-Dilithiopentane, and 1,6-dilithiohexane result.5b

Low-temperature lithium-iodine exchange between t-BuLi and a primary alkyl iodide is more rapid than lithium-bromine exchange with aryl bromides.51 Indeed, the iodine exchange reaction is so facile that it is sometimes possible to conduct preparatively useful lithium-iodine exchange in the presence of other reactive functional groups1 such as ketones (eq 23).52 Metal-halogen exchange-initiated intramolecular conjugate additions have also been reported53 (eq 24).53b

Dehalogenation of vicinal diiodides initiated by exchange with t-BuLi has been used to access highly strained alkenes54 such as cubene (eq 25).55

Addition of Carbon-Carbon Double Bonds.

In the presence of ethers or amines, t-BuLi adds rapidly to ethylene at -25 °C at 1 atm of pressure to give neohexyllithium (3,3-dimethylbutyllithium) in quantitative yield (eq 26).56 It should be noted that neohexyllithium may unexpectedly result from addition of t-BuLi to the ethylene generated from the decomposition of diethyl ether15 or THF16 when these solvents are present in reaction mixtures containing t-BuLi.56

Addition of t-BuLi to other carbon-carbon double bonds is not a facile process unless: (1) the p-system is conjugated1,57 (in which case anionic polymerization may result),58 (2) the alkene is at least somewhat strained (eq 27),59 (3) the resulting anion is stabilized as in vinylsilanes,60 vinylphosphines,61 and the like (eq 28),62 (4) a good leaving group is present at the allylic position,63 or (5) there is intramolecular assistance provided by a suitably placed heteroatom6 (eq 29).64

At high temperatures, alkyllithiums have been observed to alkylate aromatic rings by addition to the p-system and subsequent loss of LiH.1,65 Of the butyllithiums, t-BuLi has been found to be more reactive than either of its isomers in the alkylation of naphthalene and other condensed aromatics.66 Addition of t-BuLi, as well as other organolithiums, across the azomethine linkage of pyridine and similar nitrogen heterocycles is a facile process.1

Addition to Carbon-Heteroatom Multiple Bonds.

The behavior of t-BuLi in reactions with carbon-heteroatom p-bonds is relatively unremarkable and parallels that of other organolithium reagents.1 Even in cases where steric hindrance might be expected to lead to difficulties, product yields are reasonable. Thus, for example, tri-t-butylcarbinol (3-t-butyl-2,2,4,4-tetramethyl-3-pentanol) may be prepared by addition of t-BuLi to di-t-butyl ketone (2,2,4,4-tetramethyl-3-pentanone), although there is a significant amount of reduction in this case,67 and N-lithio-di-t-butylimines may be generated by addition of t-BuLi to t-butyl cyanide.68

Related Reagents.

n-Butyllithium; s-Butyllithium.

1. (a) Wakefield, B. J. The Chemistry of Organolithium Compounds; Pergamon: New York, 1974. (b) Wakefield, B. J. Organolithium Methods; Academic: San Diego, 1988. (c) Wardell, J. L. In Comprehensive Organometallic Chemistry; Wilkinson, G., Ed.; Pergamon: Oxford, 1982, Vol. 1, pp 44-120. (d) Wakefield, B. J. In Comprehensive Organic Chemistry; Barton, D. H. R.; Ollis, W. D., Eds.; Pergamon: Oxford, 1979, Vol. 3, pp 943-967.
2. Gschwend, H. W.; Rodriguez, H. R. OR 1979, 26, 1.
3. Gilman, H.; Morton, J. W., Jr. OR 1954, 8, 258.
4. Snieckus, V. CRV 1990, 90, 879.
5. (a) Bailey, W. F.; Punzalan, E. R. JOC 1990, 55, 5404. (b) Negishi, E.; Swanson, D. R.; Rousset, C. J. JOC 1990, 55, 5406.
6. Klumpp, G. W. RTC 1986, 105, 1.
7. (a) Köttke, T.; Stälke, D. AG(E) 1993, 32, 580. (b) Bates, T. F.; Clarke, M. T.; Thomas, R. D.; JACS 1988, 110, 5109.
8. (a) Thomas, R. D.; Clarke, M. T.; Jensen, R. M.; Young, T. C. OM 1986, 5, 1851. (b) Weiner, M.; Vogel, G.; West, R. IC 1962, 1, 654.
9. Stanetty, P.; Koller, H.; Mihovilovic, M. JOC 1992, 57, 6833.
10. (a) Bauer, W.; Winchester, W. R.; Schleyer, P. v. R. OM 1987, 6, 2371. (b) Settle, F. A.; Haggerty, M.; Eastham, J. F. JACS 1964, 86, 2076.
11. Langer, A. W. Adv. Chem. Ser. 1974, 130, 1.
12. (a) Kamienski, C. W.; Esmay, D. L. JOC 1960, 25, 1807. (b) Smith, W. N.; JOM 1974, 82, 1.
13. Watson, S. C.; Eastham, J. F. JOM 1967, 9, 165.
14. (a) Collins, P. F.; Kamienski, C. W.; Esmay, D. L.; Ellestad, R. B. Anal. Chem. 1961, 33, 468. (b) Crompton, T. R. Chemical Analysis of Organometallic Compounds; Academic: New York, 1973. (c) Kofron, W. G.; Baclawski, L. M. JOC 1976, 41, 1879. (d) Lipton, M. F.; Sorensen, C. M.; Sadler, A. C.; Shapiro, R. H. JOM 1980, 186, 155. (e) Winkle, M. R.; Lansinger, J. M.; Ronald, R. C. CC 1980, 87. (f) Bergbreiter, D. E.; Pendergrass, E. JOC 1981, 46, 219. (g) Juaristi, E.; Martinez-Richa, A.; Garcia-Rivera, A.; Cruz-Sanchez, J. S. JOC 1983, 48, 2603.
15. (a) Maercker, A.; Demuth, W. AG(E) 1973, 12, 75. (b) Maercker, A. AG(E) 1987, 26, 972.
16. (a) Jung, M. E.; Blum, R. B. TL 1977, 43, 3791. (b) Bates, R. B.; Kroposki, L. M.; Potter, D. E. JOC 1972, 37, 560.
17. Köhler, F. H.; Hertkorn, N.; Blümel, J. CB 1987, 120, 2081.
18. West, R. Adv. Chem. Ser. 1974, 130, 120.
19. West, R.; Jones, P. C. JACS 1969, 91, 6156.
20. Mallan, J. M.; Bebb, R. L. CRV 1969, 69, 693.
21. (a) Brandsma, L.; Verkruijsse, H. Preparative Polar Organometallic Chemistry, I; Springer: Berlin, 1987. (b) Brandsma, L. Preparative Polar Organometallic Chemistry, II; Springer: Berlin, 1987.
22. (a) Baldwin, J. E.; Höfle, G. A.; Lever, O. W. JACS 1974, 96, 7125. (b) Schöllkopf, U.; Hänssle, P. LA 1972, 763, 208.
23. Boeckman, R. K.; Bruza, K. J. TL 1977, 4187.
24. Soderquist, J. A.; Hassner, A. JOC 1980, 45, 541.
25. Oshima, K.; Shimodi, K.; Takahashi, H.; Yamamoto, H.; Nozaki, H. JACS 1973, 95, 2694.
26. Vlattas, I.; Vecchia, L. D.; Lee, A. O. JACS 1976, 98, 2008.
27. Dolak, T. M.; Bryson, T. A. TL 1977, 23, 1961.
28. (a) Schmidt, R. R.; Talbiersky, J. AG(E) 1976, 15, 171. (b) Schmidt, R. R.; Talbiersky, J. AG(E) 1977, 16, 853. (c) Schmidt, R. R.; Talbiersky, J. AG(E) 1978, 17, 204.
29. Bindal, R. D.; Katzenellenbogen, J. A. JOC 1987, 52, 3181.
30. Muchowski, J. M.; Venuti, M. C. JOC 1980, 45, 4798.
31. Riant, O.; Samuel, O.; Kagan, H. B. JACS 1993, 115, 5835.
32. (a) Jones, R. G.; Gilman, H. OR 1951, 6, 339. (b) Jones, R. G.; Gilman, H. CRV 1954, 54, 835. (c) Schöllkopf, U. MOC, 1970, 13/1, 1.
33. Applequist, D. E.; O'Brien, D. F. JACS 1963, 85, 743.
34. Corey, E. J.; Beames, D. J. JACS 1972, 94, 7210.
35. (a) Seebach, D.; Neumann, H. CB 1974, 107, 847. (b) Neumann, H.; Seebach, D. CB 1978, 111, 2785. (c) Lee, S. H.; Schwartz, J. JACS 1986, 108, 2445.
36. (a) Köbrich, G.; Trapp, H. CB 1966, 99, 680. (b) Köbrich, G. AG(E) 1967, 6, 41.
37. Ref. 1(b), pp 29 and 137.
38. Marek, I.; Lefrancois, J.-M.; Normant, J.-F.; SL 1992, 633.
39. (a) Kowalski, C. J.; O'Dowd, M. L.; Burke, M. C.; Fields, K. W. JACS 1980, 102, 5411. (b) Kowalski, C. J.; Fields, K. W. JACS 1982, 104, 1777.
40. Gadwood, R. C.; Rubino, M. R.; Nagarajan, S. C.; Michel, S. T. JOC 1985, 50, 3255.
41. Bailey, W. F.; Patricia, J. J. JOM 1988, 352, 1.
42. (a) Bailey, W. F.; Patricia, J. J.; Nurmi, T. T.; Wang, W. TL 1986, 27, 1861. (b) Bailey, W. F.; Patricia, J. J.; Nurmi, T. T. TL 1986, 27, 1865. (c) Ashby, E. C.; Pham, T. N.; Park, B. TL 1985, 26, 4691. (d) Ashby, E. C.; Pham, T. N. JOC 1987, 52, 1291.
43. Bailey, W. F.; Nurmi, T. T.; Patricia, J. J.; Wang, W. JACS 1987, 109, 2442.
44. Reich, H. J.; Green, D. P.; Phillips, N. H. JACS 1991, 113, 1414.
45. Bailey, W. F.; Khanolkar, A. D.; Gavaskar, K.; Ovaska, T. V.; Rossi, K.; Thiel, Y.; Wiberg, K. B. JACS 1991, 113, 5720.
46. (a) Bailey, W. F.; Patricia, J. J.; Del Gobbo, V. C.; Jarret, R. M.; Okarma, P. J. JOC 1985, 50, 1999. (b) Bailey, W. F.; Khanolkar, A. D. JOC 1990, 55, 6058. (c) Bailey, W. F.; Khanolkar, A. D. T 1991, 47, 7727. (d) Bailey, W. F.; Khanolkar, A. D. OM 1993, 12, 239.
47. (a) Bailey, W. F.; Khanolkar, A. D.; Gavaskar, K. V. JACS 1992, 114, 8053. (b) Bailey, W. F.; Rossi, K. JACS 1989, 111, 765.
48. (a) Bailey, W. F.; Ovaska, T. V. JACS 1993, 115, 3080. (b) Bailey, W. F.; Ovaska, T. V. TL 1990, 31, 627. (c) Wu, G.; Cederbaum, F. E.; Negishi, E. TL 1990, 31, 493. (d) Bailey, W. F.; Ovaska, T. V.; Leipert, T. K. TL 1989, 30, 3901.
49. (a) Krief, A.; Barbeaux, P. CC 1987, 1214. (b) Krief, A.; Barbeaux, P. SL 1990, 511. (c) Krief, A.; Barbeaux, P. TL 1991, 32, 417.
50. (a) Bailey, W. F.; Gagnier, R. P.; Patricia, J. J. JOC 1984, 49, 2098. (b) Bailey, W. F.; Gagnier, R. P. TL 1982, 23, 5123.
51. Beak, P.; Allen, D. J. JACS 1992, 114, 3420.
52. Cooke, M. P., Jr.; Houpis, I. N. TL 1985, 26, 4987.
53. (a) Cooke, M. P., Jr. JOC 1984, 49, 1144. (b) Cooke, M. P. Jr.; Widener, R. K. JOC 1987, 52, 1381. (c) Cooke, M. P. Jr. JOC 1992, 57, 1495. (d) Cooke, M. P., Jr. JOC 1993, 58, 2910.
54. Schäfer, J.; Szeimies, G. TL 1988, 29, 5253.
55. Eaton, P. E.; Maggini, M. JACS 1988, 110, 7230.
56. (a) Bartlett, P. D.; Friedman, S.; Stiles, M. JACS 1953, 75, 1771. (b) Bartlett, P. D.; Stiles, M. JACS 1955, 77, 2806. (c) Bartlett, P. D.; Tauber, S. J.; Weber, W. P. JACS 1969, 91, 6362. (d) Bartlett, P. D.; Goebel, C. V.; Weber, W. P. JACS 1969, 91, 7425.
57. (a) Glaze, W. H.; Jones, P. C. CC 1969, 1434. (b) Fraenkel, G.; Estes, D. W.; Geckle, M. J. JOM 1980, 185, 147. (c) Fraenkel, G.; Geckle, J. M. JACS 1980, 102, 2869. (d) Hallden-Abberton, M.; Engelman, C.; Fraenkel, G. JOC 1981, 46, 538.
58. Morton, M. Anionic Polymerization: Principles and Practice; Academic: New York, 1983.
59. Mulvaney, J. E.; Gardlund, Z. G. JOC 1965, 30, 917.
60. (a) Cason, L. F.; Brooks, H. G. JACS 1952, 74, 4582. (b) Jones, P. R.; Lim, T. F. O. JACS 1977, 99, 2013. (c) Auner, N. JOM 1987, 336, 59.
61. Peterson, D. J. JOC 1966, 31, 950.
62. Seebach, D.; Bürstinghaus, R.; Gröbel, B-T.; Kolb, M. LA 1977, 830.
63. (a) Bailey, W. F.; Zartun, D. L. CC 1984, 34. (b) Mioskowski, C.; Manna, S.; Falck, J. R. TL 1984, 25, 519.
64. Kool, M.; Klumpp, G. W. TL 1978, 21, 1873.
65. Reetz, M. T.; Schinzer, D. AG(E) 1977, 16, 44.
66. (a) Dixon, J. A.; Fishman, D. H.; JACS 1963, 85, 1356. (b) Dixon, J. A.; Fishman, D. H.; Dudinyak, R. S. TL 1964, 12, 613. (c) Eppley, R. L.; Dixon, J. A. JACS 1968, 90, 1606.
67. Bartlett, P. D.; Lefferts, E. B. JACS 1955, 77, 2804.
68. (a) Summerford, C.; Wade, K.; Wyatt, B. K. JCS(A) 1970, 2016. (b) Clegg, W.; Snaith, R.; Shearer, H. M. M.; Wade, K.; Whitehead, G. JCS(D) 1983, 1309.

William F. Bailey & Nanette Wachter-Jurcsak

University of Connecticut, Storrs, CT, USA

Copyright 1995-2000 by John Wiley & Sons, Ltd. All rights reserved.