R. Knorr
FULL PAPER
[17]
[33] For 1H NMR (CCl4), see: S. Satoh, T. Taguchi, M. Itoh, M.
Tokuda, Bull. Chem. Soc. Jpn. 1979, 52, 951–952, compound
3b therein.
Ketene 2 was not generated from 5 under these conditions; this
follows from the absence in Scheme 2 of the tBu2CD deriva-
tives, which arise from 2 (Scheme 5) in the same environment.
[34] Determinations of kinetic reaction orders were deemed imprac-
ticable: Small concentrations of the catalyst 3 would continu-
ally decrease through its side reaction with ketene 2 leading
to the anhydride 5, whereas higher concentrations of 3 would
consume a major part of 2 at the expense of the formation of
ester 4 from 2.
[35] W. A. Pryor, H. T. Bickley, J. Org. Chem. 1972, 37, 2885–2893.
[36] J. K. Crandall, S. A. Sojka, J. B. Komin, J. Org. Chem. 1974,
39, 2172–2175.
[37] A. Tille, H. Pracejus, Chem. Ber. 1967, 100, 196–210.
[38] J. Jähme, C. Rüchardt, Tetrahedron Lett. 1982, 23, 4011–4014.
[39] C. E. Cannizzaro, K. N. Houk, J. Am. Chem. Soc. 2004, 126,
10992–11008.
[40] P. J. Lillford, D. P. N. Satchell, J. Chem. Soc. B 1968, 889–897.
[41] D. P. N. Satchell, M. J. F. Satchell, Z. Naturforsch., B 1991, 46,
391–392, and earlier work cited therein.
[18]
[19]
[20]
For a literature survey, see: C. M. Hull, T. W. Bargar, J. Org.
Chem. 1975, 40, 3152–3154.
The mathematical formula usually employed to calculate kH/
kD from these data is reported in the Supporting Information.
For the feasibility of generating the sulfonium ylide in similar
systems, see: A. H. Fenselau, J. G. Moffat, J. Am. Chem. Soc.
1966, 88, 1762–1765.
A small kH/kD value would also result when the C–H and C–
D bond fissions were reversible (elimination via a kinetically
more stable sulfonium ylide whose subsequent O–S bond fis-
sion would limit the overall rate); this would eventually lead to
D/H incorporation at sulfoxide functions and thus to a de-
creased degree of labeling of the methylthio groups derived
therefrom. However, the corresponding –SCH2D or –SCHD2
groups were never detected in the present work, as exemplified
in Figure S1 of the Supporting Information.
a) L. Horner, P. Kaiser, Justus Liebigs Ann. Chem. 1959, 626,
19–25; b) J. H. Jones, D. W. Thomas, R. M. Thomas, M. E.
Wood, Synth. Commun. 1986, 16, 1607–1610.
M. Cocivera, V. Malatesta, K. W. Woo, A. Effio, J. Org. Chem.
1978, 43, 1140–1145.
[21]
[42] “A relatively high ionizing power” was confirmed on p. 11394
of ref.[11]
[22]
[43] At this point, the previously[9] proposed addition of the potas-
sium alkoxide of HOCH(tBu)C(=O)tBu (pivaloin) to 2 in
DMSO solution was now established through the in situ obser-
vation (1H NMR analysis) of the emerging pivaloin ester[9]
tBu2CHCO2CH(tBu)C(=O)tBu at ambient temperature within
approximately 3 h.
[23]
[24]
For NMR spectroscopic data, see: a) J. R. Gauvreau, S. Poi-
gnant, G. J. Martin, Tetrahedron Lett. 1980, 21, 1319–1322; b)
L. C. Ducati, M. P. Freitas, C. F. Tormena, R. Rittner, J. Mol.
Struct. 2006, 800, 45–50; c) S. W. Bass, S. A. Evans, J. Org.
Chem. 1980, 45, 710–715.
[44] S. H. Kabir, H. R. Seikaly, T. T. Tidwell, J. Am. Chem. Soc.
1979, 101, 1059–1060.
[45] The pKa = 7.04 for 3 in H2O/H3COH (1:1) at 40 °C, as reported
by: M. S. Newman, T. Fukunaga, J. Am. Chem. Soc. 1963, 85,
1176–1178.
[25] A. D. Allen, T. T. Tidwell, J. Am. Chem. Soc. 1987, 109, 2774–
2780.
[26] Compound [α-D]3, with a deuterium content of 23%, was reco-
vered from a solution of unlabeled 3 in D2SO4 at 70 °C after
53 min; compare Equation (5) in ref.[25]
[27] R. Rätz, O. J. Sweeting, J. Org. Chem. 1963, 28, 1612–1616.
[28] G. A. Olah, M. Alemayehu, A. Wu, O. Farooq, G. K. S. Prak-
ash, J. Am. Chem. Soc. 1992, 114, 8042–8045.
[29] As a low-speed example, p-xylene became acylated by an acyl-
ium reagent Ar–CϵO+ within a few hours at room tempera-
ture, apparently without decarbonylation according to Figure 7
in: F. Effenberger, J. K. Eberhard, A. H. Maier, J. Am. Chem.
Soc. 1996, 118, 12572–12579.
[46] This interpretation is based on the discovery that less encum-
bered ketenes add weak carboxylic acids at 25 °C with rates
that increase with higher pKa values, that is, with decreasing
acidities, as reported by: a) J. M. Briody, P. J. Lillford, D. P. N.
Satchell, J. Chem. Soc. B 1968, 885–889; b) N. L. Poon, D. P. N.
Satchell, J. Chem. Res. Synop. 1983, 182–183.
[47] This conclusion implies that the protonation step 1Ј should be
effectively irreversible in the acidic environment that contains
the acid 3. In support of this notion of a very slow deproton-
ation of 13, the base-free deprotonation of acetylium
(H3CCϵO+) at 150 °C to generate H2C=C=O was reported to
require 20 h; see: G. A. Olah, E. Zadok, R. Edler, D. H. Adam-
son, W. Kasha, G. K. S. Prakash, J. Am. Chem. Soc. 1989, 111,
9123–9124.
[30] For comparisons with faster Friedel–Crafts processes, the de-
carbonylation of Alk–CϵO+ was apparently either (a) faster
than, (b) similarly fast, or (c) slower than the acylation of ben-
zene by Alk–CϵO+ to give Alk–COPh; see: a) M. E. Grundy,
W.-H. Hsü, E. Rothstein, J. Chem. Soc. 1958, 581–586 for
tBuCH2CH(tBu)–CϵO+; b) G. A. Olah, W. S. Tolgyesi, S. J.
Kuhn, M. E. Moffatt, I. J. Bastien, E. B. Baker, J. Am. Chem.
Soc. 1963, 85, 1328–1334 for tBu–CϵO+; c) G. A. Olah, M. B.
Comisarov, J. Am. Chem. Soc. 1966, 88, 4442–4447, on pp.
4446–4447 for adamantyl-1-CϵO+.
[48] S. K. Bur, A. Padwa, Chem. Rev. 2004, 104, 2401–2432.
[49] O. DeLucchi, U. Miotti, G. Modena, Org. React. 1991, 40,
157–405.
[50] J. P. Marino, M. Neisser, J. Am. Chem. Soc. 1981, 103, 7687–
7689.
[51] J. P. Marino, G. Cao, Tetrahedron Lett. 2006, 47, 7711–7713.
[52] N. L. Poon, D. P. N. Satchell, J. Chem. Soc. Perkin Trans. 2
1983, 1381–1383.
[53] I. Lillien, J. Org. Chem. 1964, 29, 1631–1632.
[54] W. Adam, A. Alzérreca, J.-C. Liu, F. Yany, J. Am. Chem. Soc.
1977, 99, 5768–5773, on p. 5772.
[55] Acylium cations are the thermodynamically favored isomers in
both the gas phase and in solution, as noted on page 2778 of
ref.[25]
[31] K. K. Wang, Z. Wang, P. D. Sattsangi, J. Org. Chem. 1996, 61,
1516–1518, on p. 1518.
[32] a) For 1H NMR (CDCl3), see: R. J. Abraham, M. Canton, M.
Reid, L. Griffiths, J. Chem. Soc. Perkin Trans. 2 2000, 803–812,
Table 2 therein; b) for 13C NMR (CDCl3), see: C. W. Fong,
Aust. J. Chem. 1980, 33, 1291–1300, Table 1 therein; c) for 13C
NMR (C6D6), see: L. Ernst, Tetrahedron Lett. 1974, 15, 3079–
3080.
Received: June 28, 2011
Published Online: September 13, 2011
6342
www.eurjoc.org
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2011, 6335–6342