Aryllithiums with increasing steric crowding and lipophilicity prepared from chlorides in diethyl ether. the first directly prepared room-temperature-stable dilithioarenes

Article abstract of DOI:10.1021/ol302672n

A convenient procedure has been developed for the preparation of synthetically useful, room-temperature-stable aryllithiums starting from aryl chlorides and lithium metal. The method provides a route to aryllithiums which have previously not been accessible cleanly or could only be prepared by using more expensive starting materials.

Full text of DOI:10.1021/ol302672n

ORGANIC
LETTERS
2012
Vol. 14, No. 22
5680–5683
Aryllithiums with Increasing Steric
Crowding and Lipophilicity Prepared
from Chlorides in Diethyl Ether.
The First Directly Prepared
Room-Temperature-Stable Dilithioarenes
Constantinos G. Screttas,* Barry R. Steele, Maria Micha-Screttas, and
Georgios A. Heropoulos
Institute of Biology, Medicinal Chemistry and Biotechnology,
National Hellenic Research Foundation, Athens 11635, Greece
kskretas@eie.gr
Received September 27, 2012
ABSTRACT
A convenient procedure has been developed for the preparation of synthetically useful, room-temperature-stable aryllithiums starting from aryl
chlorides and lithium metal. The method provides a route to aryllithiums which have previously not been accessible cleanly or could only be
prepared by using more expensive starting materials.
The introduction of alkyl-substituted aryl groups is
often required for the synthesis of functional compounds
or materials intended for special applications. For exam-
ple, molecules with sterically hindered coordination sites
are frequently employed as ligands in catalysis,1 while
(1) (a) Kuhn, K. M.; Grubbs, R. H. Org. Lett. 2008, 10, 2075–2077.
(b) Schrock, R. R.; Hoveyda, A. H. Angew. Chem., Int. Ed. 2003, 38,
(3) (a) Beak, P.; McKinnie, B. G. J. Am. Chem. Soc. 1977, 99, 5213.
(b) Beak, P.; Baillargeon, M.; Carter, L. G. J. Org. Chem. 1978, 43, 4255.
(c) Beak, P.; Carter, L. G. J. Org. Chem. 1981, 46, 2363. (d) Kapeller,
D. C.; Hammerschmidt, F. J. Org. Chem. 2009, 74, 2380. (e) Larouche-
Gautier, R.; Fletcher, C. J.; Couto, I.; Aggarwal, V. Chem. Commun.
2011, 47, 12592.
(4) (a) Pushparajah, D. S.; Umachandran, M.; Nazir, T.; Plant, K. E.;
Plant, N.; Lewis, D. F.; Ioannides, C. Toxicol. In Vitro 2008, 22, 128. (b)
Fang, H.; Tong, W.; Shi, L. M.; Blair, R.; Perkins, R.; Branham, W.;
Hass, B. S.; Xie, Q.; Dial, S. L.; Moland, C. L.; Sheehan, D. M. Chem.
Res. Toxicol. 2001, 14, 280. (c) Skretas, G.; Meligova, A. K.; Villalonga-
Barber, C.; Mitsiou, D. J.; Alexis, M. N.; Micha-Screttas, M.; Steele,
B. R.; Screttas, C. G.; Wood, D. W. J. Am. Chem. Soc. 2007, 129, 8443.
(d) Villalonga-Barber, C.; Meligova, A. K.; Alexi, X.; Steele, B. R.;
Kouzinos, C. E.; Screttas, C. G.; Katsanou, E. S.; Micha-Screttas, M.;
Alexis, M. N. Bioorg. Med. Chem. 2011, 19, 339. (e) Shau, A. K.; Barstad,
D.; Radek, J. T; Meyers, M. J.; Nettles, K. W.; Katzenellenbogen, B. S.;
Katzenellenbogen, J. A.; Agard, D. A.; Greene, G. L. Nat. Struct. Biol.
2002, 9, 359.
ꢀ
4592. (c) Dıez-Gonzalez, S.; Nolan, S. P. Coord. Chem. Rev. 2007, 251,
´
874. (d) Surry, D. S.; Buchwald, S. L. Angew. Chem., Int. Ed. 2008, 47,
6338. (e) Organ, M.; Chass, G.; Fang, D. C.; Hopkinson, A.; Valente, C.
ꢀ
ꢀ
ꢀ
Synthesis 2008, 2776. (f) Gomez-Suarez, A.; Ramon, R. S.; Songis, O.;
Slawin, A. M. Z.; Cazin, C. S. J.; Nolan, S. P. Organometallics 2011, 30,
5463. (g) Qian, X.; Dawe, L. N.; Kozak, C. M. Dalton Trans. 2011, 40,
933. (h) Bouyahyi, M.; Ajellal, N.; Kirillov, E.; Thomas, C. M.;
Carpentier, J.-F. Chem.;Eur. J. 2011, 17, 1872.
(2) (a) Bouhadir, G.; Bourissou, D. Chem. Soc. Rev. 2004, 33, 210. (b)
Balazs, L.; Breunig, H. J. Coord. Chem. Rev. 2004, 248, 603. (c) Yoshifuji,
ꢀ
M. Pure Appl. Chem. 2005, 77, 2011. (d) Escudie, J.; Ranaivonjatovo, H.
Organometallics 2007, 26, 1542. (e) Wang, Y.; Robinson, G. H. Chem.
Commun. 2009, 5201. (f) Mizuhata, Y.; Sasamori, T.; Tokitoh, N. Chem.
Rev. 2009, 109, 3479. (g) Fischer, R. C.; Power, P. P. Chem. Rev. 2010, 110,
3877. (h) Stasch, A.; Jones, C. Dalton Trans. 2011, 40, 5659. (i) Sarish,
S. P.; Sen, S. S.; Roesky, H. W.; Objartel, I.; Stalke, D. Chem. Commun.
2011, 47, 7206. (j) Huynh, K.; Chun, C. P.; Lough, A. J.; Manners, I.
Dalton Trans. 2011, 40, 10576.
r
10.1021/ol302672n
Published on Web 10/31/2012
2012 American Chemical Society

bulky alkyl-substituted aryl groups are commonly used to
stabilize compounds with unusual valency or low oxida-
tion states.2 In organic synthesis, an example of their utility
is the R-lithiation of highly hindered benzoate esters to
provide lithioalkyl alcohol synthons.3 They may also
render requisite lipophilicity to biologically active mole-
cules or contribute to space-filling requirements for effec-
tive functioning.4 There is therefore a need for versatile
synthetic methodologies for the functionalization of poly-
alkylated arenes, particularly where conventional aro-
matic substitution routes fail to give satisfactory results
due to rearrangement, disproportionation, or loss of alkyl
groups.5 This issue can be a more serious problem for
secondary or tertiaryalkylgroupsand in these cases special
conditions must often be employed.6
A possible synthetic route tothe desired derivatives is via
appropriate organolithiums. The commonly used method
for the preparation of aryllithiums (ArLi) is by halogenꢀ
metal exchange, usually from the corresponding bromides.7
The generation of ArLi directly from the metal is seldom
employed, and it is notable that the majority of direct routes
to ArLi in the comprehensive compilation by Schlosser also
start from the bromides.8 The use of chlorides in the direct
synthesis of ArLi by reductive lithiation in THF is known
but it requires low to very low reaction temperatures.9 Con-
version of chlorides to polyalkylated phenyllithiums, in
particular, remains somewhat unexplored although there
is a considerable cost benefit and many chlorides are also
readily prepared by chlorinating the corresponding hydro-
carbons by the method of Hojo and Masuda.10
Lewis base.12 For polymethylated chlorobenzenes, the
electronegative substituent also enhances the carbon acid-
ity of adjacent methyls leading to complications due to the
formation of benzylic carbanions. Another problem asso-
ciated with THF in the conversion of aryl chlorides and
sulfides13 of pronounced electron affinity to ArLi is that
they form stable radical anions which either do not undergo
carbonꢀheteroatom bond fission (a prerequisite for
lithiative cleavage14) or follow other pathways. We reasoned
that Et2O, which exhibits a very low Lewis basicity, would
be a better medium for the direct synthesis of ArLi from
chlorides. It has been shown to be appropriate for the
cleavage of allylic phenyl sulfides,15 and phenylthioalkanes
(under catalysis by naphthalene)16 to provide organolithium
reagents. It may also be noted that methyl tert-butyl ether
has been used as an additive in the preparation of secondary
and tertiary alkyllithiums from the chlorides in pentane.17
In Et2O, aryl chlorides react slowly with Li chips but very
rapidly with Li dispersion. The use of Li dispersion, however,
presents some difficulties. Weighing milligram quantities, for
example, requires an inert atmosphere. Here we report a
simple method for the preparation of a form of lithium with a
particle size ranging from about 0.3 mm down to the size of
Li dispersion. These are formed by addition of Li pieces
under argon to warm mineral oil containing a small amount
of cholesterol and then heating to 210ꢀ230 °C with vigorous
magnetic stirring. After cooling, removal of the oil and then
washing with hexane leaves shiny particles of Li metal. Their
size was determined by measurement under a microscope of
the larger particles and comparison of the smallest particles
with those from a lithium dispersion. This form of Li can be
handled briefly in air and is active enough so that, upon
contact with a dilute solution of naphthalene in Et2O, it
begins to reduce it to the dianion within 20ꢀ30 s. Since this
form of the metal is distinctly different from Li shot,18 we use
the term lithium spherules.
Although simple aryl chlorides react readily with lithium
chips in THF, the reaction appears to be complicated,
judging from the plethora of species formed upon deriva-
tization. Problems may arise from benzyne formation as
a result of the ortho-directing ability of the chlorine
substituent,11 or the activation of the metalating ability
of the initial ArLi by THF which is a relatively strong
Starting from the chlorides, we have synthesized a series
of ArLi with increasing numbers of methyl and 2-ethylpropyl
groups as well as the 1,3,5-triisopropylphenyl derivative.
We also studied the dichlorides of mesitylene and durene as
well as some chloronaphthalenes and chlorostilbenes. In
special cases, preformed dilithium naphthalene dianion in
Et2O was employed as the source of Li. As electrophiles we
have applied CO2, paraformaldehyde, DMF, ClCO2Et, and
ClCOCO2Et, the last being of interest since, not only does it
provide a method of acylation where conventional electro-
philic acylation may not applicable, but also because the
(5) (a) Hennion, G. F.; Anderson, J. G. J. Am. Chem. Soc. 1946, 68,
424. (b) Smith, L. I.; Rosenbaum, J. J. J. Am. Chem. Soc. 1951, 73, 3843.
(c) Baddeley, G.; Holt, G.; Makar, S. M. J. Chem. Soc. 1952, 3289. (d)
Mosby, W. L. J. Am. Chem. Soc. 1952, 74, 2564. (e) Bartlett, P. D.; Roha,
M.; Stiles, R. M. J. Am. Chem. Soc. 1954, 76, 2349. (f) Hart, H.; Fish,
R. W. J. Am. Chem. Soc. 1961, 83, 4460. (g) Burgstahler, A. W.; Chien,
P.; Abdel-Rahman, M. O. J. Am. Chem. Soc. 1964, 86, 5281. (h)
Andreou, A. D.; Bulbulian, R. V.; Gore, P. H. Tetrahedron 1980, 36,
2101. (i) Fry, A. J.; Solomon, S. Org. Prep. Proced. Int. 1991, 23, 425. (j)
Saleh, S. Tetrahedron 1998, 54, 14157.
(6) (a) Pearson, D. E.; Frazer, M. G.; Frazer, V. S.; Washburn, L. C.
Synthesis 1976, 621. (b) Steele, B. R.; Micha-Screttas, M.; Screttas, C. G.
Tetrahedron Lett. 2004, 45, 9537.
(7) Organometallics in Synthesis: A Manual, 2nd ed.; Schlosser, M.,
Ed.; John Wiley and Sons Ltd.: Chichester, 2002; pp 118ꢀ131.
(8) Organometallics in Synthesis: A Manual, 2nd ed.; Schlosser, M.,
Ed.; John Wiley and Sons Ltd.: Chichester, 2002; pp 90ꢀ91.
(13) Screttas, C. G.; Micha-Screttas, M. J. Org. Chem. 1979, 44, 713.
(14) Screttas, C. G. J. Chem. Soc., Chem. Commun. 1972, 869.
(15) Screttas, C. G.; Heropoulos, G. A.; Micha-Screttas, M.; Steele,
B. R. Tetrahedron Lett. 2005, 46, 4357.
(16) Screttas, C. G.; Heropoulos, G. A.; Micha-Screttas, M.; Steele,
B. R.; Catsoulacos, D. P. Tetrahedron Lett. 2003, 44, 5633.
(17) Morrison, R. C.; Hall, R. W.; Schwindeman, J. A.; Kamienski,
C. W.; Engel, J. F. Eur. Patent 0525881, 1993.
(18) Fieser, L. F.; Fieser, M. Reagents for Organic Synthesis; Wiley
and Sons: New York, 1967; Vol. 1, p 570.
(19) (a) Grison, C.; Coutrot, F.; Coutrot, P. Tetrahedron 2002, 58,
2735. (b) Li, G.; Liang, Y.; Antilla, J. C. J. Am. Chem. Soc. 2007, 129,
5830. (c) Roberts, J. L.; Chan, C. Tetrahedron Lett. 2002, 43, 7679. (d)
Coutrot, P.; Grison, C.; Coutrot, F. Synlett 1998, 393. (e) Reddy, L. R.;
Gupta, A. P. J. Org. Chem. 2011, 76, 3409.
(9) (a) Screttas, C. G. Chem. Commun. 1972, 752. (b) Huerta, F. F.;
Gomez, C; Yus, M. Tetrahedron 1999, 55, 4043. (c) Yus, M.; Ramon,
D. J.; Gomez, I. Tetrahedron 2003, 59, 3219. (d) Azzena, U.; Dettori, G.;
Pisano, L.; Siotto, I. Tetrahedron 2005, 61, 3177. (e) Azzena, U.; Dettori,
G.; Sforazzini, G.; Yus, M.; Foubelo, F. Tetrahedron 2006, 62, 1557. (f)
Garcia, D.; Foubelo, F.; Yus, M. Heterocycles 2009, 77, 991 and
references therein.
(10) Hojo, M.; Masuda, R. Synth. Commun. 1975, 5, 169.
(11) Organometallics in Synthesis: A Manual, 2nd ed.; Schlosser, M.,
Ed.; John Wiley and Sons Ltd.: Chichester, 2002; p 251.
(12) (a) Screttas, C. G.;Eastham, J. F. J. Am. Chem. Soc. 1965, 87, 3276.
(b) Screttas, C. G.; Eastham, J. F. J. Am. Chem. Soc. 1966, 88, 5668.
Org. Lett., Vol. 14, No. 22, 2012
5681

R-ketoesters produced are precursors for interesting and
useful R-amino acids19 or R-hydroxy acids.20
is not very stable at room temperature (Table 2, entry 8).
This reagent reacts in Et2O with gaseous CO2 to give a
hexane-soluble lithium 2,4,6-tris(1-ethylpropyl)benzoate.
After hydration, this highly lipophilic salt is no longer
re-extractable into hexane.
Chlorotoluenes react readily with Li spherules in Et2O at
ice bath temperatures (3ꢀ6 °C) and afford tolyllithiums in
high yields (Table 1) within 1ꢀ3 h, while for Li chips up to 20 h
are needed for comparable results. Additional methyls do not
cause any appreciable drop in reactivity and the chloroxylenes,
chloromesitylene, chlorodurene and chloropentamethylben-
zene gave similar results. Entries 7 and 9 in Table 1 indicate the
long-term stability of the organolithiums in solution. These
results may be contrasted with those using THF. Reaction of
mesityl chloride with Li chips and derivatization with allyl
bromide gave 3 major products: mesitylene, 35%, 2,4,6-
trimethylallylbenzene, 40%, and 1-chloro-2-buten-3-yl-4,6-
dimethylbenzene, 14%, along with 12 minor products.
The presence of three isopropyl or two 1-ethypropyl
groups in the ring considerably diminishes the reactivity
toward lithium spherules in Et2O. In these cases, however,
catalysis by naphthalene was found to reduce the reaction
time to 3ꢀ4 h (Table 2).
Table 2. Naphthalene-Catalyzed Direct Lithiation of
Substituted Chlorobenzenes
temp time
yielda
(h) product (%)
entry
Ar
(°C)
1 pentamethylphenyl
rt
4
A
A
A
A
A
B
A
A
B
A
86
98
67
76
65
91
86
0
2 2,3,5,6-tetramethylphenyl
3ꢀ6
3
3 3,4-bis(1-ethylpropyl)phenylb 3ꢀ6
4 2,4-bis(1-ethylpropyl)phenylb 3ꢀ6
5 2,5-bis(1-ethylpropyl)phenylb 3ꢀ6
1.5
4
3
6 2,4,6-triisopropylphenyl
7 2,4,6-triisopropylphenyl
3ꢀ6
3ꢀ6
2
2.5
8 2,4,6-tris(1-ethylpropyl)phenyl rt
23
9 2,4,6-tris(1-ethylpropyl)phenyl 3ꢀ6 3c
85
60
Table 1. Reaction of Aryl Chlorides with Li Spherules in Et2O
10 2,4,6-tris(1-ethylpropyl)phenyl 3ꢀ6 3c
a Isolated yields. b CuCN added to organolithium prior to addition of
electrophile. c 2 h at 3ꢀ6 °C þ 1 h at rt.
temp
timea
(h)
yieldb
(%)
1,3-Dichloro-2,4,6-trimethylbenzene and 1,4-dichloro-
2,3,5,6-tetramethylbenzene react with Li spherules to give
mixtures of 3 possible products (Scheme 1) which were
inferred by conversion to the oxoaceates and analyzed by
GC-MS. Obviously the stability of 1 and 3, as well as 4 and
6, is due to the fact that the halogen or lithium substituents
are flanked by methyl groups which preclude benzyne
formation. These constitute the first examples of the gen-
eration of room temperature stable solutions of methyl-
substituted dilithiobenzenes directly from chlorides. Pre-
vious reports have involved bromides and iodides and
halogenꢀmetal interconversion.21
entry
Ar
(°C)
1
2
2-tolyl
3-tolyl
4-tolyl
3ꢀ6
3ꢀ6
3ꢀ6
3ꢀ6
3ꢀ6
3ꢀ6
rt
3
3
91
86
95
99
95
99
77
86
81
80
0c
3
3
4
2,6-dimethylphenyl
3.75
4.5
3
5
2,5-dimethylphenyl
6
2,4,6-trimethylphenyl
2,3,5,6-tetramethylphenyl
pentamethylphenyl
7
22
4
8
rt
9
pentamethylphenyl
rt
22
19
23
10
11
3,4-bis(1-ethylpropyl)phenyl
2,4,6-tris(1-ethylpropyl)phenyl
rt
rt
a Reaction time for formation of organolithium. b Isolated yields.
c 77% of starting material recovered.
Scheme 1. Direct Lithiation of Aryl Dichlorides
1-Chloro-2,4,6,-tris(1-ethylpropyl)benzene gave good
yields only under catalysis with naphthalene (Table 2,
entries 9 and 10). In the uncatalyzed reaction, 73% of the
aryl chloride was recovered unchanged after 23 h at room
temperature, while the remainder was dehalogenated to
the hydrocarbon (Table 1, entry 11). Complete dehalo-
genation takes place even under catalysis for longer reaction
times, indicating that 2,4,6-tris(1-ethylpropyl)phenyllithium
The reaction of the dichlorides with preformed dilithium
naphthalene dianion22 leads to the dilithiated and dehalo-
monolithiated products 2, 3 and 5, 6 (Table 3). 1-Chloro-
2,4,6-tris(1-ethylpropyl)benzene could alsobeconvertedin
good yield by this route (Table 3, entry 1).
(20) For recent examples, see: (a) Pennacchio, A.; Rossi, M.; Raia,
C. A.; Giordano, A. Eur. J. Org. Chem. 2011, 4361. (b) Ni, Y.; Li, C.-Y.;
Wang, L.-J.; Zhang, J.; Xu, J.-H. Org. Biomol. Chem. 2011, 9, 5463. (c)
Balazsik, K.; Szri, K.; Gyoergy, B. M. Chem. Commun. 2011, 47, 1551.
(21) Fossatelli, M.; den Besten, R.; Verkruijsse, H. D.; Brandsma, L.
Recl. Trav. Chim. Pays-Bas 1994, 113, 527and references therein.
(22) Dilithium naphthalene dianion in Et2O appears to be quite
stable at room temperature, in contrast to the situation with THF.
See: Yus, M.; Herrera, R. P.; Guijarro, A. Chem.;Eur. J. 2002, 8, 2574.
Yus, M.; Herrera, R. P.; Guijarro, A. Tetrahedron Lett. 2001, 42, 3455.
(23) Petrov, A. D.; Nefedov, O. M.; Vorobyev, V. D. Russ. Chem. Bull.
1957, 6, 1129. Vesely, S. Collect. Czech. Chem. Commun. 1932, 4, 139.
5682
Org. Lett., Vol. 14, No. 22, 2012

Table 3. Reactions with Dilithium Naphthalene Dianion
Table 4. Aryllithiums from Chloronaphthalenes and
Chlorostilbenes in Et2Oa
entry
Ar
time (h) product yield (%)
1
2
1-naphthylb
2-naphthyl
3
3
A
B
A
A
A
B
B
C
B
B
C
72
28
3
1-(2-methyl)naphthyl
1-(4-methyl)naphthyl
1-(2-methoxy)naphthyl
1-(2-methoxy)naphthyl
(5,6,7,8-tetrahydro)naphthylc
2-styrylphenyl
4
53
4
4
35
5
2
82
6
3
80
88 (40/48)d
76
7
2.5
20
20
3
8
9
2-styrylphenyl
70
10
11
3-styrylphenyl
78
e
4-styrylphenyl
22
a All reactions carried out at rt unless otherwise stated. b Contained
13% 2-chloronaphthalene. c 40/60 mixture of 1- and 2-isomers. Reaction
carried out at 3ꢀ6 °C with prior formation of cuprate. d GC yields. e Very
complex mixture.
may arise because the pKa of MeOH is lower than that of
2-naphthol in Et2O.
Methyland methoxyderivativesof1-chloronaphthalene
were also investigated. 1-Chloro-2-methylnaphthalene gave
good yields of 1-lithio-2-methylnaphthalene (entry 3), while
1-chloro-4-methylnaphthalene gave rather low yields of the
corresponding naphthyllithium (entry 4). 1-Chloro-2-meth-
oxynaphthalene reacted cleanly and afforded good yields of
1-lithio-2-methoxynaphthalene (entries 5,6). Obviously this
is due to the difference in cleavability between CꢀCl and
CꢀO bonds in favor of the former. An approximately
40ꢀ60% mixture of 1- and 2-chlorotetralin gave a good
overall yield of the corresponding ArLi which were char-
acterized as ethyl 2-oxoacetates (entry 7). We also investi-
gated the chlorostilbenes which tend to form radical anions
and dianions even more readily. Indeed, 2-chloro- and
3-chlorostilbenes reacted with Li spherules in Et2O to afford
good yields of the corresponding lithiostilbenes (entries
8ꢀ10) although 4-chlorostilbene only gave a complex mix-
ture of products (entry 11). It is stressed that 2-phenylthio-
and 2-methoxynaphthalene as well as the chloronaphtha-
lenes and chlorostilbenes fail to react cleanly with Li in THF
for reasons already mentioned.13
Reports on the synthesis of 1-naphthyllithium from
1-chloronaphthalene are scarce,23 while no analogous report
was found for 2-naphthyllithium. 1-Chloronaphthalene reacts
readily with Li spherules in Et2O with apparent rapid dissolu-
tion of the metal and after 2ꢀ3 h at room temperature affords
fair yields of 1-naphthyllithium (Table 4, entry 1). The
dissolution of the metal and the initial purple color of the
solution suggest the intermediacy of the 1-chloronaphthalene
dianion. This is favored by the poor solvating ability of Et2O; it
is known that addition of the weakly solvating Et2O or Et3N
to THF solutions of alkali metal naphthalene radical anions
causes disproportionation to naphthalene and its dianion.24
2-Chloronaphthalene gave poor yields of 2-naphthyl-
lithium (entry 2), and considering its high price, we
sought alternative starting materials for the synthesis
of 2-naphthyllithium and examined the lithiative cleav-
age of 2-phenylthionaphthalene, 2-methoxynaphthalene,
2-trimethylsilyloxynaphthalene, tri-2-naphthyl phosphate,
and 2-naphthyl tosylate. Of these, only the PhS and MeO
derivatives reacted with Li spherules in Et2O to give fair
yields of 2-naphthyllithium. The cleavage of 2-methoxy-
naphthalene to 2-naphthyllithium and LiOMe rather than
to MeLi and lithium 2-naphthoxide is somewhat unexpected.
Assuming that the CꢀO cleavage reaction path is governed
by the thermochemical stability of the fragments,13 this result
In conclusion, we have developed a convenient procedure
for the preparation of synthetically useful, room tempera-
ture stable aryllithiums which have previously not been
accessible cleanly or only by using more expensive starting
materials.
Supporting Information Available. Full experimental
details, mass spectra, and 1H and 13C NMR spectra. This
material is available free of charge via the Internet at
http://pubs.acs.org.
(24) Screttas, C. G.; Micha-Screttas, M. J. Org. Chem. 1983, 48, 153.
The authors declare no competing financial interest.
Org. Lett., Vol. 14, No. 22, 2012
5683