Reaction of diisobutylaluminium hydride with selenium and tellurium: New reagents for the synthesis of seleno- and telluro-amides

Article abstract of DOI:10.1039/a707792k

Diisobutylaluminium hydride (Bu^I₂AlH) undergoes reaction with elemental selenium and tellurium to afford new reagents having an Al-Se or an Al-Te bond. These directly convert amides to selenoamides and telluroformamides. This affords

Full text of DOI:10.1039/a707792k

View Article Online / Journal Homepage / Table of Contents for this issue
Reaction of diisobutylaluminium hydride with selenium and tellurium:
new reagents for the synthesis of seleno- and telluro-amides
Guang Ming Li* and Ralph A. Zingaro
Department of Chemistry, Texas A & M University, College Station, TX 77843-3255, USA
Diisobutylaluminium hydride (Bui2AlH) undergoes reaction with elemental selenium and tellurium to
afford new reagents having an Al᎐Se or an Al᎐Te bond. These directly convert amides to selenoamides and
telluroformamides. This affords a one-pot route to selenoamides and telluroformamides starting from Se
and Te, and may be suitable for large scale syntheses.
O
Introduction
E
(BuiAlE)n
Selenoamides have proved to be useful compounds in organic
transformations and several methods for their preparation
have been reported.1 There has been a considerable interest
in their tellurium analogs, viz., telluroamides, with respect to
their syntheses, structures and reactivities. Telluroamides,
like other tellurocarbonyl compounds, are difficult to prepare
R
NR1R2
toluene
Bui2AlH
E = Se, Te
(Bui2AlE)2
C-E-Al type
R
NR1R2
+
E
toluene
1–15
Se
Se
N
Se
due to the instability of the C᎐Te bond. To date, only a very
᎐
limited number of telluroamides2 and their first metal com-
plexes3 have been described. Among currently active studies
in the field of organo-selenium and -tellurium chemistry,4
bis(dimethylaluminium) selenide and telluride, (Me2Al)2E where
E is Se or Te, have been found to be effective reagents for the
conversion of carbonyl groups to seleno- and telluro-
N
H
H
N
O
H
MeN
1
2
3
Se
Se
Se
Ph
Ph
Me
Ph
Bu
Ph
carbonyls (C᎐E).2b,c,5 Using this procedure, we have success-
N
N
N
N
H
H
H
᎐
fully synthesized two telluroamides and determined their crys-
tal structures.2c In this paper,6 we report a one-pot synthesis of
seleno- and telluro-amides by the reaction of amides with
some new Al᎐Se and Al᎐Te reagents (Scheme 1). These
reagents are prepared by the reaction between diisobutyl-
aluminium hydride and selenium or tellurium powders. They
are obtained as a mixture of (Bui2AlE)2 and (BuiAlE)n where
E is Se or Te.
6
4
5
Se
Se
Se
Me
Me
Me
Me
N
N
Ph
H
Me
Me
Me
7
8
9
Te
Te
Se
Results and discussion
N
N
H
H
N
O
Under an argon atmosphere, a mixture of Bui2AlH (1.5 ) solu-
tion in toluene, 10 ml, 15 mmol) and one equivalent of pow-
dered selenium or tellurium was heated at 120–130 ЊC for 1–2 h.
All of the Se or Te was dissolved. There was first produced a
clear colorless solution7 in the case of Se, which subsequently
converted to a white suspension when cooled below 90 ЊC. A
white suspension7 was obtained when Te was used. During the
heating, gaseous evolution was observed.8 Mass spectrometry
confirmed that the gases were hydrogen and isobutane which
indicated the formation of dimer (Bui2AlE)2 and oligomer
(BuiAlE)n.
Me
10
11
Te
12
Te
Te
Me
Ph
Me
Me
N
N
H
H
N
H
MeN
13
14
15
Scheme 1
The products obtained in the reaction between Se and
1H and 13C NMR spectra are due to the presence of a mix-
ture of several Al᎐Se compounds formed in the reaction.
In the 77Se NMR spectra (in C6D6–toluene), two peaks
(δ Ϫ184.53, Ϫ263.37 ppm) were observed. They arise from
two different Al᎐Se compounds, (BuiAlSe)n and (Bui2AlSe)2.
These shifted to δ Ϫ211.64 and Ϫ430.27 ppm when THF was
added.9
These results suggest that the reaction between diisobutyl-
aluminium hydride and selenium and tellurium produces a
mixture of (Bui2AlE)2 and (BuiAlE)n (E is Se or Te) together
with a small amount of C᎐E᎐Al type compounds.
1
Bui2AlH were characterized by NMR spectrometry. In the H
spectra, compared with Bui2AlH, the reaction mixture exhib-
ited resonances at the same region except for the presence of
a small doublet at δ 2.65 ppm arising from the CH2 bonded
to Se. This indicates that only a small amount of selenium
inserts into the C᎐Al bond of Bui2AlH to form C᎐Se᎐Al type
compounds. Most of the selenium inserts between aluminium
and the hydride hydrogen. Seven doublets for methyl and
1
methylene protons of Bui groups appeared in the H NMR
spectra, and eight different carbon resonances were observed
in the 13C NMR spectra (Fig. 1). The relatively complicated
Owing to their instability, toxicity, and extremely unpleasant
J. Chem. Soc., Perkin Trans. 1, 1998
647

View Article Online
odor, these reagents were neither purified nor fully character-
ized. We have begun to investigate their reactivities. As listed in
Table 1, these reagents prepared in situ undergo reaction with
amides and efficiently convert them to seleno- and telluro-
data. Tellurium compounds (11–15) gave the expected spectral
data, but because of decomposition during delivery they did
not give acceptable elemental analyses. Seleno- and telluro-
formamides (1–7 and 11–14) were isolated in yields of 49–69%.
However, N,N-dimethyl(selenoacetamide) 8 and a γ-seleno-
lactam, 1-methyl-2-selenoxopyrroline 10 were obtained in lower
yields. N,N-dimethyl(selenobenzamide) 9 was isolated in only
30% yield, even under much more vigorous reaction conditions.
All attempts to prepare N,N-dimethyl(telluroacetamide) and
N,N-dimethyl(tellurobenzamide) were unsuccessful. This is
probably because the CH3 of N-acetyl or the Ph of N-benzoyl
hindered the attack from Al᎐Se or Al᎐Te reagents into the
carbonyl group.
1
amides 1–15. In addition, Bui2E2, which was identified by H
NMR and mass spectrometry, was isolated in all cases in 5–10%
yields.7 Compounds 2, 4, 6, 7, 12 and 14 are the same as those
obtained with the use of (Me2Al)2E.2b,c,3 All selenoamides gave
the expected NMR (1H, 13C, 77Se), mass spectral and analytical
Both the reagents described in this paper, (Bui2AlE)2 and
(BuiAlE)n where E is Se or Te, and the closely related analog
(Me2Al)2E are good for the conversion of amides to seleno-
amides and telluroformamides. The former are much easier to
prepare. The yields of selenoamides and telluroformamides
obtained in the present work are generally lower than that
prepared by the procedure using (Me2Al)2E.2b,c However, 4-
(telluroformyl)morpholine (12) was obtained almost in the same
yield: 66% in this work and 69.5% when (Me2Al)2Te was used.
In addition, (Me2Al)2E compounds are useful for the prepar-
ation of selenoaldehydes, selenoketones, telluroaldehydes and
telluroketones.5 Further investigations on the utilization of the
reagents (Bui2AlE)2 and (BuiAlE)n are in progress.
In conclusion, the present procedure provides a convenient
synthetic route for the preparation of a variety of selenoamides
and telluroformamides, and can easily be adapted to large
scale syntheses with proper safety precautions in handling large
amounts of diisobutylaluminium hydride toluene solutions.
Experimental
General
THF was refluxed over potassium metal and distilled under
argon prior to use. All other chemicals were used as received.
1H and 13C NMR spectra were recorded on a Varian XL-200
1
spectrometer (200.1 MHz for H, 50.3 MHz for 13C). 77Se and
125Te NMR spectra were measured on a Varian XL-200 broad-
band spectrometer (38.2 MHz for 77Se, 63.1 MHz for 125Te)
with Ph2Se2 (δ 460 ppm referenced to Me2Se)10a or Ph2Te2
(δ 420.8 referenced to Me2Te) 10b as the external standards.
Mass spectra were run using a VG-70S spectrometer in the
ϩFAB/DP or EI/DP mode. Melting points were determined on
a Fisher-Johns melting point apparatus and are uncorrected.
Elemental analyses were performed by Galbraith Laboratories,
1
Fig. 1 (a) H and (b) 13C NMR spectra of Al᎐Se reagents formed in
the reaction of Bui2AlH and Se (measured in C6D6–toluene, 200.1 Hz
for 1H; 50.3 Hz for 13C)
Table 1 Preparation of seleno- and telluro-amides (1–15) from amidesa
Reaction conditions
ЊC
60–70
h
Product
Form
Mp (ЊC)
Yield (%)b
4
4
3
3
3
4
3
5
12
4
3
3
3
3
1
2
yellow solid
yellow solid
yellow oil
yellow oil
yellow oil
yellow solid
yellow oil
yellow solid
orange solid
red oil
orange-red solid
orange-red solid
red oil
deep purple oil
deep red oil
45.0–47.0
77.0–78.0
65.5
69
64
64
63
60–70
60–70
60–70
60–70
60–70
60–70
60–70
100–110
60–70
20–30
20–30
20–30
20–30
20–30
3
4
5
6c
7
128.0–130.0
60
58.8
34.6
30
41
50
66
49
51
25
8
9
78.0–80.0
49.0–50.0
10
11
12
13
14
15
50.0–55.0 (decomp.)
83.0–85.0 (decomp.)
3
a All reactions were performed on a 15 mmol scale (10 ml of 1.5  Bui2AlH toluene solution, 15 mmol of Se or Te, and 15.5 mmol of an amide).
b Isolated yield based on Se or Te. c The starting material, N,N-diphenylformamide, was dissolved in 5 ml of THF (dry) prior to adding to the
suspension (Al᎐Se reagents in toluene).
648
J. Chem. Soc., Perkin Trans. 1, 1998

View Article Online
Inc (USA) and Canadian Microanalytical Service, Ltd
(Canada).
this, 15.5 mmol of an amide was added at room temperature.
The mixture was stirred at 20–30 ЊC for 3 h, and then evapor-
ated. The telluroamide was isolated by flash column chromato-
graphy on Florisil with hexane followed by CH2Cl2 as the
solvents.11
General procedure for one-pot synthesis of selenoamides
A mixture of selenium (1.185 g, 15 mmol) and Bui2AlH (1.5 
in toluene, 10 ml, 15 mmol) was heated at 120–130 ЊC for
1 h under argon, and then cooled to room temperature. To
this, 15.5 mmol of the appropriate amide was added. The
mixture was stirred under the conditions shown in Table 1.
Following evaporation, the residue was chromatographed on
Silica gel column with hexane followed by CH2Cl2 as the
solvents.11 Evaporation of the eluate gave the corresponding
selenoamides.
1-(Selenoformyl)piperidine 1. m/e (ϩFAB mode) 178
([M ϩ H]ϩ, 80Se) (Anal. Calcd for C6H11NSe: C, 40.92; H,
6.30; N, 7.95. Found: C, 40.96; H, 6.28; N, 7.96%); δH(CDCl3)
10.26 (s, 1H), 3.78 (br s, 2H), 3.36 (br s, 2H), 1.45 (br s, 6H);
δC(CDCl3) 186.35, 58.24, 48.29, 25.60, 23.83, 22.80; δSe(CDCl3)
496.1.
1-(Telluroformyl)piperidine 11. m/e (ϩFAB mode) 227 (Mϩ,
130Te); δH(C6D6) 12.52 (s, 1H), 3.69 (t, 2H), 2.48 (t, 2H), 1.05–
1.25 (m, 2H), 0.70–1.00 (m, 4H); δC(C6D6) 177.03, 61.28, 55.00,
25.11, 24.62, 23.33; δTe(C6D6) 511.2.
4-(Telluroformyl)morphline 12. Full analytical and spectral
data have been reported in ref. 3.
4-Methyl-1-(telluroformyl)piperazine 13. m/e (ϩFAB mode)
242 (Mϩ, 130Te); δH(C6D6) 12.61 (s, 1H), 3.84 (t, 2H), 2.60 (t,
2H), 1.90 (t, 2H), 1.77 (s, 3H), 1.64 (t, 2H); δC(C6D6) 178.66,
59.99, 54.09, 54.04, 53.01, 44.91; δTe(C6D6) 542.5.
N-Methyl(telluroformanilide) 14. δTe(C6D6) 875.3. For other
spectral data, see ref. 2b.
N,N-Dimethyl(telluroformamide) 15. m/e (EI mode) 187
(Mϩ, 130Te); δH(C6D6) 12.47 (br s, 1H), 2.76 (s, 3H), 2.12 (s, 3H);
δC(C6D6) 179.92, 49.57, 46.13; δTe(C6D6) 598.9.
4-(Selenoformyl)morphline 2. All analytical and spectral data
have been reported previously.3
4-Methyl-1-(selenoformyl)piperazine 3. m/e (ϩFAB mode)
193 ([M ϩ H]ϩ, 80Se) (Anal. Calcd for C6H12N2Se: C, 37.70; H,
6.33; N, 14.66. Found: C, 37.61; H, 6.20; N, 13.99%); δH(CDCl3)
10.61 (s, 1H), 4.13 (t, 2H), 3.62 (t, 2H), 2.45–2.55 (m, 4H), 2.32
(br s, 3H); δC(CDCl3) 189.02, 57.46, 54.71, 53.40, 48.12, 45.50;
δSe(CDCl3) 535.2.
N-Methyl(selenoformanilide) 4. m/e (ϩFAB mode) 200
([M ϩ H]ϩ, 80Se) (Anal. Calcd for C8H9NSe: C, 48.50; H, 4.58;
N, 7.07. Found: C, 49.13; H, 4.66; N, 7.12%); δH(CDCl3) 11.17
(s, 1H), 7.30–7.50 (m, 3H), 7.20–7.30 (m, 2H), 3.76 (s, 3H).
δC(CDCl3) 192.38, 147.06, 129.72, 127.77, 121.48, 41.71;
δSe(CDCl3) 696.6.
N-Butyl(selenoformanilide) 5. m/e (ϩFAB mode) 242
([M ϩ H]ϩ, 80Se) (Anal. Calcd for C11H15NSe: C, 55.00; H, 6.29;
N, 5.83. Found: C, 54.98; H, 6.31; N, 5.71%); δH(CDCl3) 11.04
(s, 1H), 7.30–7.50 (m, 3H), 7.15–7.30 (m, 2H), 4.37 (t, 2H),
1.50–1.80 (m, 2H), 1.20–1.50 (m, 2H), 0.90 (t, 3H); δC(CDCl3)
192.28, 146.06, 129.77, 128.06, 122.77, 52.93, 28.21, 19.91,
13.67; δSe(CDCl3) 651.4.
Acknowledgements
This work was supported by grants from the Robert A. Welch
Foundation (Houston, TX, USA) and the Selenium-Tellurium
Development Association. We thank Asarco (USA) and
Noranda, Inc. (Canada) for the gifts of selenium and tellurium
powders. The reviewer’s helpful comments are highly
appreciated.
References
1 For some recent reviews: (a) A. Ogawa and N. Sonoda, in
Comprehensive Organic Synthesis, ed. E. Winterfeldt, Pergamon,
Oxford, UK, 1991, vol. 6, pp. 461–484; (b) C. P. Dell, in
Comprehensive Organic Functional Group Transformations, ed. C. J.
Moody, Pergamon, Oxford, UK, 1995, vol. 5, pp. 565–628.
2 (a) K. A. Lerstrup and L. Henriksen, J. Chem. Soc., Chem.
Commun., 1979, 1102; (b) M. Segi, A. Kojima, T. Nakajima and
S. Suga, Synlett, 1991, 2, 105; (c) G. M. Li, R. A. Zingaro, M. Segi,
J. H. Reibenspies and T. Nakajima, Organometallics, 1997, 16,
756.
N,N-Diphenyl(selenoformamide) 6. Analytical and spectral
3 G. M. Li, J. H. Reibenspies and R. A. Zingaro, Heteroatom Chem.,
in the press.
data have been reported in ref. 2c.
N,N-Dimethyl(selenoformamide) 7. m/e (EI mode) 137 (Mϩ,
80Se) (Anal. Calcd for C3H7NSe: C, 26.48; H, 5.19; N, 10.29.
Found: C, 26.92; H, 5.51; N, 10.18%); δH(CDCl3) 10.56 (br s,
1H), 3.30 (br s, 3H), 3.26 (br s, 3H); δC(CDCl3) 190.44, 47.79,
40.50; δSe(CDCl3) 553.5.
4 Some selected monographs and review articles: (a) Selenium
Reagents and Intermediates in Organic Synthesis, ed. J. E. Baldwin,
Pergamon, Oxford, UK, 1986; (b) The Chemistry of Organic
Selenium and Tellurium Compounds, ed. S. Patai and Z. Rappoport,
Wiley, New York, 1986, vol. 1; (c) The Chemistry of Organic
Selenium and Tellurium Compounds, ed. S. Patai, Wiley, New York,
1987, vol. 2; (d) K. J. Irgolic, in Houben-Weyl-Methoden der
Organischen Chemie, ed. D. Klayman, 4th edn., Georg Thieme,
Stuttgart, 1990, vol. E12b; (e) N. Petragnani, in Tellurium in Organic
Synthesis, Academic Press, New York, 1994; ( f ) A. Krief, in
Comprehensive Organometallic Chemistry II, ed. A. McKillop,
Pergamon, Oxford, UK, 1995, vol. 11, ch. 13, pp. 515–569; (g)
N. Petragnani, in ref. 4f, chapter 14, pp. 571–601; (h) F. S. Guziec, Jr.
and L. J. Guziec, in Comprehensive Organic Functional Group
Transformations, ed. G. Pattenden, Pergamon, Oxford, UK, 1995,
vol. 3, pp. 381–401.
5 (a) M. Segi, T. Koyama, Y. Takata, T. Nakajima and S. Suga, J. Am.
Chem. Soc., 1989, 111, 8749; (b) M. Segi, T. Koyama, T. Nakajima,
S. Suga, S. Murai and N. Sonoda, Tetrahedron Lett., 1989, 30, 2095;
(c) G. M. Li, M. Segi and T. Nakajima, Tetrahedron Lett., 1992, 33,
3515; (d) M. Segi, T. Takahashi, H. Ichinose, G. M. Li and
T. Nakajima, Tetrahedron Lett., 1992, 33, 7865; (e) G. M. Li,
T. Kamogawa, M. Segi and T. Nakajima, Chem. Express, 1993, 8,
53.
N,N-Dimethyl(selenoacetamide) 8. m/e (EI mode) 151 (Mϩ,
80Se) (Anal. Calcd for C4H9NSe: C, 32.01; H, 6.04; N, 9.33.
Found: C, 31.81; H, 5.79; N, 8.99%); δH(CDCl3) 3.48 (s, 3H),
3.15 (s, 3H), 2.55 (s, 3H); δC(CDCl3) 202.33, 48.29, 42.45, 36.82;
δSe(CDCl3) 620.2.
N,N-Dimethyl(selenobenzamide) 9. m/e (ϩFAB mode) 214
([M ϩ H]ϩ, 80Se) (Anal. Calcd for C9H11NSe: C, 50.95; H, 5.23;
N, 6.60. Found: C, 50.95; H, 5.66; N, 6.41%); δH(CDCl3) 7.25
(m, 5H), 3.63 and 3.61 (2 × s, 3H); 3.04 and 3.02 (2 × s, 3H);
δC(CDCl3) 204.67; 145.77, 128.10, 127.76, 124.34, 47.01, 44.54;
δSe(CDCl3) 726.1.
1-Methyl-2-selenoxopyrroline 10. m/e (ϩFAB mode) 164
([M ϩ H]ϩ, 80Se) (Anal. Calcd for C5H9NSe: C, 37.05; H, 5.60;
N, 8.64. Found: C, 37.13; H, 5.55; N, 8.30%); δH(CDCl3) 3.67
(br t, 2H), 3.32 (br s, 3H), 3.02 (br t, 2H), 2.04 (br, quintet,
2H); δC(CDCl3) 202.96, 58.68, 49.04, 38.30, 20.01; δSe(CDCl3)
372.0.
6 A part of this work has been presented at the 7th International
Conference on the Chemistry of Selenium and Tellurium (ICCST-
7), July 1997, Vaalsbroek Castle, The Netherlands.
7 By reaction with less fresh Bui2AlH toluene solution, selenium gave
a yellow solution and tellurium gave a brown-red suspension. It
needed to reflux longer (3–4 h) to dissolve all selenium or tellurium
powder, and the yields of by-product Bui2E2 (E: Se, Te) increased up
to 20%.
General procedure for one-pot synthesis of telluroamides
In an aluminium-foil-wrapped, very dry, and air-free three-
necked flask, tellurium (1.915 g, 15 mmol) and Bui2AlH (1.5 
in toluene, 10 ml, 15 mmol) was stirred at 120–130 ЊC for 2 h. To
J. Chem. Soc., Perkin Trans. 1, 1998
649

View Article Online
8 As a controlled experiment, DIBAL-H (1.5  solution in toluene)
was heated at 120–130 ЊC for 2 h, but no gas was evolved and the
NMR (1H, 13C) measurement has proved that DIBAL-H is stable
under these conditions.
11 Using hexane to remove Bui2Se2 or Bui2Te2, and then CH2Cl2 to elute
selenoamides or telluroamides. For compounds 3 and 13, acetone
was used as the final solvent.
9 In the 77Se NMR spectra, (Me2Al)2Se resonated at δ Ϫ420 ppm
under similar conditions (in [2H]8toluene–THF solution), see:
M. Segi and T. Nakajima, Yuki Gosei Kagaku Kyokai Shi, 1995, 53,
678.
Paper 7/07792K
Received 23rd September 1997
Accepted 24th November 1997
10 (a) M. Lardon, J. Am. Chem. Soc., 1970, 92, 5063; (b) P. Granger,
S. Chapelle, W. McWhinnie and A. Al-Rubaie, J. Organomet. Chem.,
1981, 220, 149.
650
J. Chem. Soc., Perkin Trans. 1, 1998