ORGANIC
LETTERS
2005
Vol. 7, No. 5
759-762
Novel Lactonization of
Ethenetricarboxylate Derivatives:
Intermolecular Trapping of Alkenes
Shoko Yamazaki,* Kanae Ohmitsu, Kunihiro Ohi, Tetsuya Otsubo, and
Kayo Moriyama
Department of Chemistry, Nara UniVersity of Education, Takabatake-cho,
Nara 630-8528, Japan
Received November 10, 2004
ABSTRACT
A novel cyclization of 1,1-diethyl 2-tert-butyl ethenetricarboxylate (1a) in the presence of a Lewis acid afforded a 5,5-dimethyl-
γ-lactone derivative
2a. The reaction process has been shown to arise from formation by trapping of isobutylene generated in situ. Lewis acid-promoted intermolecular
reactions of 1,1-diethyl 2-hydrogen ethenetricarboxylate (5) and various alkenes to afford highly functionalized γ-lactones were also developed.
Ethenetricarboxylate derivatives have been employed as
highly electrophilic C2 components in Lewis acid-promoted
[2 + 2] and [2 + 1] cycloadditions.1,2 In addition, Lewis
acid-promoted intramolecular cyclizations of ethenetricar-
boxylate esters bearing nucleophilic CdC and CtC bonds
and aromatic rings have been studied.3 As part of our efforts
to demonstrate the utility of Lewis acid-promoted reaction
of highly electrophilic ethenetricarboxylates, a highly unusual
γ-lactone formation by trapping of isobutylene generated in
situ was discovered (eq 1). Furthermore, Lewis acid-
promoted intermolecular reactions of 1,1-diethyl 2-hydrogen
ethenetricarboxylate (5) and alkenes to highly functionalized
γ-lactones were also developed.
1,1-Diethyl 2-tert-butyl ethenetricarboxylate (1a) was used
as an electrophile in Lewis acid-promoted [2 + 1] cycload-
ditions with the nucleophilic olefin 1-(phenylseleno)-2-
(trimethylsilyl)ethene.2 The reactivity of 1a in the absence
of a nucleophile and in the presence of a Lewis acid is of
interest. The reaction of 1a in the presence of SnCl4 or TiCl4
(1.2 equiv) in CH2Cl2 at room temperature for 3 h gave the
γ-lactone 2a in 71-78% yield (eq 1). The reaction of 1a at
-40 °C for 3 h also gave 2a in 75% yield. The reaction at
-78 °C for 3 h did not proceed, and starting material 1a
was recovered. The structure of 2a was suggested by the
presence of two differentiated methyl groups (1H δ 1.39 and
1.48 ppm) and the disappearance of CdCH (1H δ 6.80) and
the tert-butyl group (1H δ 1.49) in 1a. 1H, 13C, 1H/1H-COSY,
1H/13C-HSQC, HMBC, and NOESY spectra and IR spectra
(1) Srisiri, W.; Padias, A. B.; Hall, H. K., Jr. J. Org. Chem. 1994, 59,
5424.
(2) Yamazaki, S.; Kumagai, H.; Takada, T.; Yamabe, S. J. Org. Chem.
1997, 62, 2968.
(3) (a) Snider, B. B.; Roush, D. M. J. Org. Chem. 1979, 44, 4229. (b)
Yamazaki, S.; Yamada, K.; Yamabe, S.; Yamamoto, K. J. Org. Chem. 2002,
67, 2889. (c) Yamazaki, S.; Yamada, K.; Yamamoto, K. Org. Biomol. Chem.
2004, 2, 257. (d) Yamazaki, S.; Morikawa, S.; Iwata, Y.; Yamamoto, M.;
Kuramoto, K. Org. Biomol. Chem. 2004, 2, 3134.
10.1021/ol047693z CCC: $30.25
© 2005 American Chemical Society
Published on Web 02/02/2005