COMMUNICATIONS
[10] Abbreviations: Ac ¼ acetyl; Bn ¼ benzyl; DBU ¼ 1,8-diazabicy-
clo[5.4.0]undec-7-ene; DIBAL-H ¼ diisobutylaluminum hydride;
DMF ¼ N,N-dimethylformamide;
DMAP ¼ 4-dimethylaminopyri-
dine; PPTS ¼ pyridinium p-toluenesulfonate; TBS ¼ dimethyl-tert-
butylsilyl; THF ¼ tetrahydrofuran; TMS ¼ trimethylsilyl.
[11] C. D©Silva, R. Iqbal, Synthesis 1996, 457.
[12] D. A. Evans, D. S. Johnson, Org. Lett. 1999, 1, 595.
[13] For the synthesis of N-benzoylpyrrole under similar conditions, see:
F. M. Menger, J. A. Donohue, J. Am. Chem. Soc. 1973, 95, 432.
[14] H. C. Brown, S. Krishnamurty, Tetrahedron 1979, 35, 567.
[15] A quick purification is desirable for 6g, as this compound is unstable
to prolonged exposure to silica gel.
[16] The barrier to rotation about the amide bond for N-acetylpyrrole is
about 7 kcalmolꢀ1 less than for N,N-dimethylacetamide: K. Dahlqvist,
S. Forsÿn, J. Phys. Chem. 1969, 73, 4124.
[17] We thank Mr. C. Wade Downeyfor solving the X-raystructure of
6b.
[18] CCDC-185908 contains the supplementarycrystallographic data for
m.ac.uk/conts/retrieving.html (or from the Cambridge Crystallo-
graphic Data Centre, 12, Union Road, Cambridge CB21EZ, UK;
fax: (þ 44)1223-336-033; or deposit@ccdc.cam.ac.uk).
Scheme 3. Transformations of carbinols 6. a) MeLi, THF, 08C; b) TBSCl,
imidazole, CH2Cl2; c) TMSOTf, 2,6-lutidine, DMF; d) nBu4NF, THF,
ꢀ788C.
[19] a) 1.412 ä: E. Sugahara, M. M. S. Paula, I. Vencato, C. V. Franco, J.
Coord. Chem. 1996, 39, 59; b) 1.445 ä: S. Gomez, C. Vinas, M.
Lamrani, F. Teixidor, R. Kivekas, R. Sillanpaa, Inorg. Chem. 1997, 36,
3565; c) 1.452 ä: A. Bach, L. Beyer, T. Gelbrich, K. H. Hallmeier, C.
Hennig, M. Mobius, R. Richter, R. Szargan, V. Fernandez, J. Losada,
Z. Naturforsch. B 1996, 51, 757; d) 1.458 ä: see ref. [19c].
[20] F. H. Allen, O. Kennard, D. G. Watson, L. Brammer, A. G. Orpen, R.
Taylor, J. Chem. Soc. Perkin Trans. 2 1987, S1.
carbinols in good to high yields. The stability of the alkoxides
generated bydeprotonation of the carbinols depends on the
electronegativityof the counterion in the order Mg II > LiI >
NaI. Conversion of the carbinols into the corresponding
carbonyl compounds can be achieved with catalytic DBU. In
addition, we have demonstrated that pyrrolyl carbinols are
useful synthetic intermediates that are stable enough to
undergo further synthetic transformations.
ꢀ
ꢀ
[21] An elongated C N bond and a shortened C O bond were also
observed in the X-raycrsytal structure of the anionic complex
[(Ph)2(NMe2)C(OLi)¥THF]2 formed bythe addition of PhLi to N,N-
dimethylbenzamide.[4a]
Received: May22, 2002 [Z19350]
[22] Prepared in 62% yield by the condensation of N,N’-carbonyldiimida-
zole with two equivalents of pyrrole at 1258C: J. Bergman, R.
Carlsson, B. Sjˆberg, J. Heterocycl. Chem. 1977, 14, 1123.
[23] The carbinol was completelyconverted into the ketone or aldehyde in
all three reactions.
[24] The reaction was warmed rapidlyto minimize baseline drift.
[25] Solutions of 16 or 17 in THF were treated with nBuLi in hexanes
(2 equiv), MeMgCl in THF (3 equiv), DIBAL-H in hexanes (3 equiv),
and DBU in THF (3 equiv) and monitored bythin layer chromatog-
raphyat ꢀ788C, ꢀ488C, and 08C for about 45 min at each temper-
ature. Except for partial desilylation of 16 with nBuLi at 08C, no
significant decomposition was observed under these reaction con-
ditions.
[1] For discussions of the mechanism of acyl transfer reactions, see:
a) T. C. Bruice, S. J. Benkovic, Bioorganic Mechanisms, Benjamin,
New York, 1966; b) S. L. Johnson, Adv. Phys. Org. Chem. 1967, 5, 237;
c) M. L. Bender, Mechanisms of Homogeneous Catalysis from Protons
to Proteins, Wiley-Interscience, New York, 1971; d) A. J. Kirby,
Compr. Chem. Kinet. 1972, 10, 57; e) W. P. Jencks, Catalysis in
Chemistry and Enzymology, Dover, New York, 1987; f) A. Fersht,
Structure and Mechanism in Protein Science, W. H. Freeman, New
York, 1999.
[2] a) S. Nahm, S. M. Weinreb, Tetrahedron Lett. 1981, 22, 3815; b) B. T.
O©Neill in Comprehensive Organic Synthesis, Vol. 1 (Eds.: B. M. Trost,
I. Fleming, S. L. Schreiber), Pergamon Press, Oxford, 1991, p. 399.
[3] F. Wingler, Methoden Org. Chem.(Houben-Weyl) 4th ed. 1952 , Vol. 7/
2a, 1973, p. 581.
[4] For two notable examples in which an amide tetrahedral intermediate
has been isolated as the anion, see: a) M. Adler, M. Marsch, N. S.
Nudelman, G. Boche, Angew. Chem. 1999, 111, 1345; Angew. Chem.
Int. Ed. 1999, 38, 1261; b) C. Cox, H. Wack, T. Lectka, J. Am. Chem.
Soc. 1999, 121, 7963.
[5] A remarkable exception is the synthesis of a hydrated adamantyla-
mide tetrahedral intermediate byKirbyet al.: A. J. Kirb,y I. V.
Komarov, P. D. Wothers, N. Feeder, Angew. Chem. 1998, 110, 830;
Angew. Chem. Int. Ed. 1998, 37, 785.
[6] a) M. S. Taggart, G. H. Richter, J. Am. Chem. Soc. 1934, 56, 1385;
b) M. E. K. Cartoon, G. W. H. Cheeseman, J. Organomet. Chem. 1982,
234, 123; c) S. D. Lee, M. A. Brook, T. H. Chan, Tetrahedron Lett.
1983, 24, 1569; d) S. Brandange, B. Rodriguez, Acta Chem. Scand. Ser.
B 1987, 41, 740; e) S. Brandange, E. Holmgren, H. Leijonmarck, B.
Rodriguez, Acta Chem. Scand. 1995, 49, 922.
[7] E. Arai, H. Tokuyama, M. S. Linsell, T. Fukuyama, Tetrahedron Lett.
1998, 39, 71.
[8] T. D. Penning, S. W. Djuric, R. A. Haack, V. J. Kalish, J. M. Miyashiro,
B. W. Rowell, S. S. Yu, Synth. Commun. 1990, 20, 307 312.
[9] D. A. Evans, K. A. Scheidt, J. N. Johnston, M. C. Willis, J. Am. Chem.
Soc. 2001, 123, 4480.
Angew. Chem. Int. Ed. 2002, 41, No. 17
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