Preparation of alcohols from alkenes via the homologation of boronates with (trimethylsilyl)diazomethane

Article abstract of DOI:10.1021/ol005780v

(Matrix presented) Alkylcatecholboranes obtained from alkenes were converted to the corresponding alkylmethanols by reaction with (trimethylsilyl)diazomethane followed by oxidation and treatment with fluoride.

Full text of DOI:10.1021/ol005780v

ORGANIC
LETTERS
2000
Vol. 2, No. 10
1455-1456
Preparation of Alcohols from Alkenes
via the Homologation of Boronates with
(Trimethylsilyl)diazomethane
,§
Jean-Philippe Goddard, Thierry Le Gall,* and Charles Mioskowski*
CEA-Saclay, SerVice des Mole´cules Marque´es, Baˆt. 547, De´partement de Biologie
Cellulaire et Mole´culaire, F-91191 Gif-sur-YVette Cedex, France
legall@dsVidf.cea.fr
Received March 9, 2000
ABSTRACT
Alkylcatecholboranes obtained from alkenes were converted to the corresponding alkylmethanols by reaction with (trimethylsilyl)diazomethane
followed by oxidation and treatment with fluoride.
Simple procedures allowing for elongation of the carbon
chain of organic molecules are often needed in the course
of multistep syntheses. Several methods for the conversion
of alkenes to the corresponding alkylmethanols have been
described, such as the reaction of boron compounds with
carbon monoxide in the presence of a hydride, followed by
basic hydrolysis.1 Other methods involve the reaction of a
boron compound with a nucleophilic reagent possessing a
leaving group.2 The ate complex formed initially can then
rearrange to yield a homologated boron compound which
can then be oxidized to an alcohol (Scheme 1). To be of
Reagents such as dimethylsulfoxonium methylide3 or di-
methylsulfonium methylide4 lead to mixtures of homologated
and polyhomologated products. The preparation of polymers
by reaction of boron compounds with diazoalcanes5 and
dimethylsulfoxonium methylide6 has been reported. It is
possible to obtain only monohomologated compounds using
(chloromethyl)lithium or (bromomethyl)lithium generated in
the presence of a boronic ester7 or using (dichloromethyl)-
lithium followed by in situ reduction with potassium tri-
isopropoxyborohydride.8 Monohomologation is also obtain-
ed when halo(trialkylsilyl)methyllithium is reacted with
an organoborane9 or a boronate.10 After removal of the
(3) Tufariello, J. J.; Lee, L. T. C. J. Am. Chem. Soc. 1966, 88, 4757.
(4) Tufariello, J. J.; Wojtkowski, P.; Lee, L. T. C. Chem. Commun. 1967,
505.
Scheme 1
(5) (a) Meerwein, H.; Hinz, G. Liebigs Ann. Chem. 1930, 484, 1. (b)
Bawn, C. E. H.; Ledwith, A. Prog. Boron Chem. 1964, 1, 345 and references
therein.
(6) Shea, K. J.; Walker, J. W.; Zhu, H.; Paz, M.; Greaves, J. J. Am.
Chem. Soc. 1997, 119, 9049.
(7) (a) Sadhu, K. M.; Matteson, D. S. Organometallics 1985, 4, 1687.
(b) Michnick, T. J.; Matteson, D. S. Synlett 1991, 631.
(8) (a) Brown, H. C.; Singh, S. M.; Rangaishenvi, M. V. J. Org. Chem.
1986, 51, 3150. (b) Brown, H. C.; Singh, S. M. Organometallics 1986, 5,
994.
(9) Larson, G. L.; Argu¨elles, R.; Rosario, O.; Sandoval, S. J. Organomet.
Chem. 1980, 198, 15.
(10) (a) Matteson, D. S.; Majumbar, D. J. Organomet. Chem. 1980, 184,
C41. (b) Matteson, D. S; Majumbar, D. Organometallics 1983, 2, 230. (c)
Tsai, D. J. S.; Matteson, D. S. Organometallics 1983, 2, 236.
synthetic utility, it is crucial that only one homologation takes
place in the process.
§ charles.mioskowski@cea.fr.
(1) Brown, H. C.; Hubbard, J. L.; Smith, K. Synthesis 1979, 701.
(2) For reviews, see: (a) Pelter, A.; Smith, K.; Brown, H. C. Borane
Reagents; Academic Press: London, 1988. (b) Vaultier, M.; Carboni, B.
In ComprehensiVe Organometallic Chemistry; Abel, E. W., Stone, F. G.
A., Wilkinson, G., McKillop, A., Eds.; Pergamon: Oxford, 1995; Vol. 11,
pp 191-276.
10.1021/ol005780v CCC: $19.00 © 2000 American Chemical Society
Published on Web 04/20/2000

trialkylsilyl moiety, a homologated boron compound is then
obtained, which can be converted to the corresponding
alcohol.
Table 1. Alcohols 6 from Alkenes 2
In this Letter, we present the conversion of alkenes to the
corresponding alkylmethanols using as the key step the
reaction of boronates with (trimethylsilyl)diazomethane
(1),11,12 a reagent that is commercially available (Scheme 2).
Scheme 2
(Trimethylsilyl)diazomethane thus allows one to obtain
monohomologated boron compounds. Sequential treatments
of boron compounds with monohomologating agents could
in principle be employed to prepare diversely functionalized
products. To test this possibility, tributylborane in THF was
treated with excess 1 (3.6 equiv) for 24 h at room temper-
ature; then excess ethyl diazoacetate (7; 3.6 equiv) was added
and the solution was refluxed for 12 h (Scheme 3). After
Thus, alkenes 2 were treated with catecholborane at 100
°C. This hydroboration is known to place selectively the
boron atom on the less hindered carbon atom of the alkene
and to yield mainly the exo isomer from norbornene.13 After
removal of excess catecholborane, the boronates 3 obtained
were diluted in THF and heated in the presence of 3-5 equiv
of 1 for 10 h. Oxidation by alkaline H2O2 then afforded
R-(trimethylsilyl)alcohols 5, which were purified by chro-
matography. Compound 5e was obtained as a mixture of
diastereomers.
Scheme 3
Alcohols 6 were then obtained after treatment with
tetrabutylammonium fluoride, with an overall yield of 38-
63% from alkenes 2, as summarized in Table 1. A reaction
was also carried out using the recrystallized boronate
prepared from catecholborane and 4-vinylanisole. It reacted
with 1 under the conditions described above to afford, after
oxidation, silanol 5b in 63% yield and the nonhomologated
alcohol 2-(4-methoxyphenyl)ethanol in 27% yield. This
indicates that the reaction of the boronate with 1 is the step
determining the overall yield of the process, rather than the
hydroboration or the desilylation.
treatment with propionic acid, ethyl 3-(trimethylsilyl)-
heptanoate (8), resulting from two consecutive homologa-
tions, was obtained in 33% yield (based on the butyl groups
in Bu3B). Reactions starting from boron compounds having
only one transferable group will soon be evaluated.
In conclusion, we have described a practical procedure
for the preparation of alkylmethanols from alkenes which
makes use of the homologation of alkylcatecholboranes with
(trimethylsilyl)diazomethane. The method has the advantage
that no generation of lithiated species is needed, and also it
avoids the use of toxic carbon monoxide.
(11) For reviews, see: (a) Shioiri, T.; Aoyama, T. In Encyclopedia of
Reagents for Organic Synthesis; Paquette, L. A., Ed.; John Wiley and
Sons: Chichester, 1995; Vol. 7, pp 5248-5251. (b) Anderson, R.; Anderson,
S. B. In AdVances in Silicon Chemistry; Larson, G. L., Ed.; Jai Press:
London, 1991; Vol. 1, pp 303-325.
(12) The preparation of 10-trimethylsilyl-9-borabicyclo[3.3.2]decane by
reaction of (trimethylsilyl)diazomethane with B-methoxy-9-BBN followed
by reduction has been reported: Soderquist, J. A.; Matos, K.; Vaquer, J.;
Huang, S. D. Book of Abstracts, 214th National Meeting of the American
Chemical Society, Las Vegas, NV, September 7-11, 1997; American
Chemical Society: Washington, DC, 1997; ORGN-055.
Supporting Information Available: Experimental pro-
cedures and characterization data for compounds 5a-e, 6a-
e, and 8. This material is available free of charge via the
Internet at http://pubs.acs.org.
(13) Brown, H. C.; Gupta, S. K. J. Am. Chem. Soc. 1975, 97, 5249.
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Org. Lett., Vol. 2, No. 10, 2000