Communications
Pꢁrez, E. Guitiꢂn, L. Castedo, Angew. Chem. 1998, 110, 2804;
Angew. Chem. Int. Ed. 1998, 37, 2659; j) J.-M. Becht, A. Gissot, A.
Wagner, C. Mioskowski, Chem. Eur. J. 2003, 9, 3209.
[4] a) P. Knochel, W. Dohle, N. Gommermann, F. Kneisel, F. Kopp, T.
Korn, I. Sapountzis, V. A. Vu, Angew. Chem. 2003, 115, 4438;
Angew. Chem. Int. Ed. 2003, 42, 4302; b) A. Staubitz, W. Dohle, P.
Knochel, Synthesis 2003, 233; c) A. E. Jensen, W. Dohle, I.
Sapountzis, D. M. Lindsay, V. A. Vu, P. Knochel, Synthesis 2002,
565; d) N. Gommermann, C. Koradin, P. Knochel, Synthesis 2002,
2143; e) I. Sapountzis, P. Knochel, Angew. Chem. 2004, 116, 915;
Angew. Chem. Int. Ed. 2004, 43, 897.
[5] Interestingly, the magnesium derivative of methyl 4-pivaloxy-3-
iodobenzoate is also unstable and rapidly decomposes at ꢀ788C.
[6] For the preparation of Grignard reagents that bear a nitro group,
see: I. Sapountzis, P. Knochel, Angew. Chem. 2002, 114, 1680;
Angew. Chem. Int. Ed. 2002, 41, 1610.
[7] For the preparation of Grignard reagents that contain a ketone
function, see: F. F. Kneisel, P. Knochel, Synlett 2002, 1799.
[8] For the preparation of 3-(2-furyl)propionyl chloride we used
literature procedures starting from furfural: a) M. Takeuchi, T.
Taniguchi, K. Ogasawara, Synthesis 1999, 341; b) A. Robertson,
D. Philip, N. Spencer, Tetrahedron 1999, 55, 11365; c) A. Padwa,
T. J. Wisnieff, E. J. Walsh, J. Org. Chem. 1989, 54, 298.
Scheme 4. Intramolecular trapping of a functionalized aryne:
a) iPrMgCl, ꢀ788C, 0.5 h, then CuCN·2LiCl, ꢀ788C, 10 min, then 3-(2-
furyl)propionyl chloride (2 equiv, ꢀ788C!RT, 1 h); b) iPrMgCl, ꢀ788C,
0.5 h,then ꢀ788C!RT, 1 h.
In summary, we have developed a new and general
method for the preparation of functionalized arynes by the
readily tunable elimination of 2-magnesiated aryl sulfonates.
Further applications are under investigation in our laborato-
ries.
Experimental Section
Typical procedure: 4a: A dry, argon-flushed 10-mL Schlenk tube
equipped with a magnetic stirring bar and a septum was charged with
a solution of methyl iodobenzoate 2g (452mg, 1.00 mmol) in dry
THF (5 mL) and cooled to ꢀ788C. iPrMgCl (0.920 mL, 1.05 mmol,
1.10m in THF) was then added dropwise, and after 30 min furan
(0.38 mL, 5.0 mmol) was added slowly at ꢀ788C. The resulting
mixture was warmed to room temperature and stirred for a further
2h. The reaction was quenched with a saturated solution of NH 4Cl,
the mixture was extracted with CH2Cl2, and the organic extracts were
dried over Na2SO4, filtered, and concentrated in vacuo. Purification
by flash chromatography on silica gel (pentane/diethyl ether 2:1)
furnished 4a (188 mg, 93%) as a colorless solid.
[9] Besides 7 (48% yield), we also isolated an iodoketone (2-[3-(2-
furyl)propanoyl]-4-iodophenyl 4-chlorobenzenesulfonate), which
probably formed through protonation of the corresponding
Grignard reagent.
Received: April 22, 2004 [Z460417]
Keywords:
.
Grignard reagents · arynes · cycloaddition · elimination ·
metalation
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4366
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Angew. Chem. Int. Ed. 2004, 43, 4364 –4366