6
32
Can. J. Chem. Vol. 83, 2005
Fe(PMe ) (CNCH CMe ) plus nitrone dimer using benzene
as the solvent.
NMR (C D ) δ: 0.87 (t, J = 4 Hz). GC-MS (10 eV) m/z: 89
3
2
2
3 3
6
6
+
+
+
+
([M] ), 74 ([M – CH ]), 71 ([M – CD ]), 63 ([M – CN]).
3 3
Preparation of tert-butylisocyanide-d6
Preparation of Fe(PMe ) (t-BuNC-d )
3 2 6 3
The preparation of tert-butylisocyanide-d6 was accom-
plished in 3 steps using known reactions. The first step was
the synthesis of tert-butanol-d from acetone-d by a Grig-
The synthesis was the same as described previously (4)
for the protio isocyanide complex, using FeCl (0.14 g), Mg
2
6
6
(0.08 g), and PMe (103 mmHg (1 mmHg = 133.322 Pa),
3
nard reaction (15). Into a 1000 mL round bottom flask fitted
with a septum and a 50 mL addition funnel was placed
300 K, 1.056 L) in THF (50 mL) and adding 0.30 mL t-
BuNC-d6.
3
mol/L CH MgI in ether (220 mL, 0.66 mol) and 250 mL
3
of diethyl ether. The solution was cooled to 0 °C under a ni-
Isotope effect determinations
trogen atmosphere, and acetone-d (40 mL, 0.49 mol) was
6
The determination of the isotope effect was accomplished
using three separate samples prepared in resealable NMR
tubes. A benzene solution of 20 mg Fe(PMe ) (t-BuNC-d )
6 3
slowly added to the ether solution. The flask was allowed to
warm to room temperature and was stirred overnight under
nitrogen. After 18 h, the solution was again placed in an ice
bath, and 50 mL of 10% HCl (aq) was slowly added to neu-
tralize the excess MeMgI. The solution was warmed to room
3
2
was heated at 67 °C for 24 h. The volatiles were vacuum
distilled from the NMR tube to a two-neck flask equipped
with an adapter and a septum. The benzene solutions were
analyzed by GC–MS using the conditions stated above to
determine the ratio of d :d isobutylene. The three samples
temperature, and the tert-butanol-d was extracted from the
6
aqueous layer using 3 × 50 mL aliquots of diethyl ether. The
6
5
ether was removed from the combined extracts, giving tert-
showed ratios of 0.56 (0.01), 0.55 (0.02), and 0.56 (0.01).
1
butanol-d (15.8 g, 0.20 mol, 35% yield). H NMR (C D ) δ:
6
6
6
1
.06 (s). Overnight reaction is required to give reasonable
yields.
The second step was the formation of tert-butylformamide-
d from the tert-butanol-d via a Ritter reaction (16). Cau-
Acknowledgement
The US Department of Energy, Grant FG02–86ER13569
are gratefully acknowledged for their support of this work.
6
6
tion must be taken in this step because of the formation of
HCN. In a 250 mL Erlenmeyer flask, tert-butanol-d (15.8 g,
6
0
.20 mol) and potassium cyanide (15 g, 0.23 mol) were dis-
solved in 25 mL acetic acid. A solution of 25 mL H SO and
References
2
4
2
5 mL acetic acid was added dropwise over a period of 2 h
1
. J.W. Rathke and E.L. Muetterties. J. Am. Chem. Soc. 97, 3272
1975).
. (a) H.H. Karsch, H.F. Klein, and H. Schmidbaur. Chem. Ber.
10, 2200 (1977); (b) H.H. Karsch. Inorg. Synth. 20, 69
1977); (c) H.H. Karsch, H.F. Klein, and H. Schmidbaur.
to the solution, keeping the temperature below 60 °C. The
mixture was allowed to stir overnight at room temperature.
After 16 h, the mixture was poured into 500 mL of ice
water. The solution was placed in an ice bath, and 15% KOH
(
2
1
(
(
aq) was added slowly until the acid was neutralized. The
Angew. Chem. Int. Ed. Engl. 14, 637 (1975).
. (a) H.H. Karsch. Chem. Ber. 110, 2213 (1977); (b) H.H.
Karsch. Chem. Ber. 110, 2699 (1977); (c) H.H. Karsch. Chem.
Ber. 110, 2712 (1977).
pH was checked using litmus paper. The tert-
3
butylformamide-d was extracted using 5 × 100 mL portions
of diethyl ether. The ether was dried over potassium carbon-
ate overnight and then removed by distillation. Fractional
6
4. W.D. Jones, G.P. Foster, and J.M. Putinas. Inorg. Chem. 26,
2120 (1987).
5. The observed pseudotriplet arises from what has been referred
to as an AX9A′X′9 system, see: C.P. Casey, J.M. O’Conner,
W.D. Jones, and K.J. Haller. Organometallics, 2, 535 (1983).
distillation gave tert-butylformamide-d (5.9 g, 0.06 mol,
6
1
3
0% yield). bp 200 °C. H NMR (C D ) δ: 0.89 (s), 1.19 (s).
6
6
+
+
GC-MS (10 eV) m/z: 107 ([M] ), 92 ([M – CH ]), 89
3
+
(
[M – CD ]).
3
6
. W.D. Jones, G.P. Foster, and J.M. Putinas. J. Am. Chem. Soc.
, 2124 (1987).
. (a) E.G. Janzen and B.J. Blackburn. J. Am. Chem. Soc. 90,
909 (1968); (b) E.G. Janzen and B.J. Blackburn. J. Am.
The final step was the dehydration of the formamide using
7
POCl (17). Into a 250 mL round bottom flask equipped
with a 10 mL addition funnel, condenser, and a mechanical
stirrer was placed tert-butylformamide-d (5.9 g, 0.06 mol),
pyridine (30 mL, 0.37 mol), and 100 mL diethyl ether. The
3
7
5
6
Chem. Soc. 91, 4481 (1969); (c) E.G. Janzen and C.A. Evans.
J. Am. Chem. Soc. 97, 205 (1975).
solution was cooled to 0 °C in an ice bath. POCl (7 mL,
3
8
9
. (a) E. Grunwald and S. Winstein. J. Am. Chem. Soc. 70, 846
0
.09 mol) was placed into the addition funnel. After purging
(
1948); (b) J. Burgess. J. Chem. Soc. A, 2114 (1970); (c) J.
with nitrogen for 10 min, the POCl was slowly added. Care
3
Burgess. Pure Appl. Chem. 63, 1677 (1991).
. K. Wiberg. Chem. Rev. 55, 713 (1955).
must be taken to ensure rapid stirring during the addition.
The solution was allowed to warm to room temperature and
then refluxed for 1 h. The flask was again placed in an ice
bath and distilled water was added to neutralize the excess
1
1
0. J.M. Nicovich, C.A. van Dijk, K.D. Kreutter, and P.H. Wine. J.
Phys. Chem. 95, 9890 (1991).
1. W.H. Saunders and A.F. Cockerill (Editors). Mechanisms of
elimination reactions. Wiley, New York. 1973. p. 1073, and
refs. therein.
POCl and dissolve the salts that formed. The organic layer
3
was separated from the aqueous layer, and the aqueous layer
was washed with ether (5 × 50 mL). The combined organic
layers were dried over magnesium sulfate. The ether was re-
moved by distillation and tert-butylisocyanide was obtained
1
2. C.M. Giamdomenico, L.H. Hanau, and S.J. Lippard. J.
Organomet. Chem. 1, 142 (1982).
13. L. Tschugaeff and P. Teearu. Chem. Ber. 47, 2643 (1914).
14. W.D. Jones and W.P. Kosar. Organometallics, 5, 1823 (1986).
1
by vacuum distillation (0.5 mL, 0.005 mol, 8% yield). H
©
2005 NRC Canada