SnCl4-induced unsymmetrical cleavage of Bis(N,N- diethylcarbamoyltelluro)-arylmethanes: Generation of tellurobenzaldehydes

Article abstract of DOI:10.1002/hc.21115

Tellurobenzaldehydes bearing an electron-withdrawing substituent were generated by way of SnCl₄-induced unsymmetrical cleavage of bis(N,N-dialkylcarbamoyltelluro)arylmethanes, and were trapped using 2,3-dimethyl-1,3-butadiene.

Full text of DOI:10.1002/hc.21115

Heteroatom Chemistry
Volume 24, Number 6, 2013
SnCl4-Induced Unsymmetrical Cleavage of
Bis(N,N-diethylcarbamoyltelluro)-
arylmethanes: Generation of
Tellurobenzaldehydes
Kazuaki Shimada, Takumi Higashi, Yaling Gong, Shigenobu Aoyagi,
Yuji Takikawa, and Satoshi Ogawa
Department of Chemistry and Bioengineering, Faculty of Engineering, Iwate University, Morioka,
Iwate 020-8551, Japan
Received 16 May 2013; revised 11 August 2013
due to the high instability of the target species
ABSTRACT: Tellurobenzaldehydes bearing an
toward air, light, and heating, as well as the
lack of preparative methods of suitable and eas-
ily accessible precursors. In the course of our
electron-withdrawing substituent were generated
by way of SnCl4-induced unsymmetrical cleavage
of
bis(N,N-dialkylcarbamoyltelluro)arylmethanes,
studies on the novel generation of higher-row
chalcogenocarbonyl compounds, we previously re-
ported a convenient preparation of stable ditel-
luroacetal derivatives A through the reaction of
in situ generated tellurocarbamate ions with gem-
dihaloalkanes [9–11]. Actually, such ditelluroac-
etals A are recognized as potent precursors for
telluroaldehydes B in the light of their symmetri-
cal structures with an easily removable electron-
withdrawing carbamoyl group on each tellurium
atom, and compouds A are expected to undergo
SnCl4-induced unsymmetrical C–Te bond cleav-
age to generate telluroaldehydes B through push–
pull type removal of N,N-diethyltellurocarbamate
in an analogous manner of our previous report on
the generation of selenoaldehydes from bis(N,N-
dimethylcarbamoylseleno)methanes [12, 13]. Ac-
cording to our expectation as mentioned above, we
started our exploration on the reaction of A with
SnCl4 in the presence or absence of trapping agents.
In this paper, we describe a new method for gener-
ation of tellurobenzaldehydes B from precursors A
bearing an electron-withdrawing substituent on the
aryl group.
and were trapped using 2,3-dimethyl-1,3-butadiene.
ꢀC
2013 Wiley Periodicals, Inc. Heteroatom Chem.
24:482–489, 2013; View this article online at
wileyonlinelibrary.com. DOI 10.1002/hc.21115
INTRODUCTION
Recently, a wide variety of studies on thio- and
selenoaldehydes have been achieved in the light
of their structural interests and the potential-
ity as new reactive intermediates for the organic
reactions [1–4]. However, only limited research
works on generation, trapping, or metal complex-
ation of telluroaldehydes B were reported [5–8]
Correspondence to: Kazuaki Shimada; e-mail: shimada@iwate-
u.ac.jp.
ꢀC
2013 Wiley Periodicals, Inc.
482

SnCl4-Induced Unsymmetrical Cleavage of Bis(N,N-diethylcarbamoyltelluro)arylmethanes 483
RESULTS AND DISCUSSION
p-chlorobenzal bromide (3c), 2,4,6-trimethylbenzal
chloride (3d), p-fluorobenzal chloride (3e), and p-
trifluoromethylbenzal chloride (3f), respectively). All
the results of the one-pot synthesis of 4 and 5 are
shown in Table 1.
Preparation of Bis(N,N-
dialkylcarbamoyltelluro)arylmethanes (1, 4, 5,
R1 = CH3 or C2H5)
Bis(N,N-dimethylcarbamoyl) ditelluride (1) was
at first prepared in moderate yield by treating
N,N-dimethylformamide (DMF) with sodium and
elemental tellurium under heating followed by aero-
bic oxidation of the reaction mixture [9–13]. Prepa-
ration of bis(N,N-diethylcarbamoyl) ditelluride (2,
R1 = C2H5) was also carried out by treating N,N-
diethylformamide (DEF) with lithium metal and el-
emental tellurium through a similar procedure as
shown in Scheme 1. However, ditelluride 2 was
unstable on the contact with silica gel, and was
only used for the further reactions without purifi-
cation. Subsequently, when ditelluride 1 was sub-
jected to sodium borohydride (NaBH4) reduction in
ethanol followed by treatment with substituted ben-
zal bromides (3), the corresponding ditelluroacetals
4 bearing a N,N-dimethylcarbamoyl group on each
tellurium atom were obtained in moderate yields
according to our previous reports [14–18]. In con-
trast, a similar treatment of crude ditelluride 2 with
NaBH4 and 3 only gave a complex mixture in which
a trace amount of the corresponding ditelluroacetals
5 was contained.
Reaction of Bis(N,N-dialkylcarbamoyltelluro)-
arylmethanes (4, 5) with SnCl4 in the Presence
of Dienes
Treating a Dichloromethane (CH2Cl2), a chloro-
form (CHCl3), or a benzene solution of bis(N,N-
dimethylcartbamoyltellluro)phenylmethane
(4a,
R2 = C6H5) with SnCl4 (2.0 mol) at room tem-
perature (R.T.) under an Argon atmosphere in the
presence of 2,3-dimethyl-1,3-butadiene, cyclopen-
tadiene, or Danishefsky’s diene only afforded a
complex mixture along with extrusion of elemental
tellurium in the reaction mixture and no products
related to the corresponding [4+2] cycloadducts
of tellurobenzaldehydes B were found at all in the
crude mixture. Similar unsuccessful results were
obtained through the reaction started from bis(N,N-
diethylcartbamoyltellluro)phenylmethane
(5a,
R2 = C6H5) bearing a bulky N,N-diethylcarbamoyl
group on each tellurium atom or from bis(N,N-
diethylcarbamolytelluro)mesitylmethane (5d, R2 =
2,4,6-trimethylphenyl (Mes)) bearing a bulky aryl
group for the steric protection of telluroaldehydes.
In contrast, when substrate 5e (R2 = p-FC6H4)
or 5f (R2 = p-CF3C6H4) bearing an electron-
withdrawing group on the aryl group was applied
to the same reactions in a benzene solution at R.T.,
In contrast, the yields of ditelluroacetals 4 and
5 were successfully improved by using a conve-
nient one-pot procedure starting from DMF or DEF
[(i) Na or Li metal; (ii) elemental tellurium, 110◦C,
2 h; and (iii) substituted benzal halides 3 (i.e., ben-
zal bromide (3a), m-chlorobenzal bromide (3b),
SCHEME 1 Preparation of (1) bis(N,N-dimethylcarbamoyl) ditelluride and (2) bis(N,N-diethylcarbamoyl) ditelluride.
Heteroatom Chemistry DOI 10.1002/hc

484 Shimada et al.
TABLE 1 One-Pot Synthesis of Bis(N,N-dialkylcarbamoyltelluro)methanes (4, 5)
R2CHX2 / 3
R1
Na or Li
Temp (◦C)
Time 1 (h)
R2
X
Time 2 (h)
Product 4, 5
Yield (%)
CH3
Na
Li
Li
Li
Li
Li
Li
100
110
110
110
110
110
110
1
2
2
2
2
2
2
C6H5
C6H5
m-ClC6H4
H
Mes
p-FC6H4
p-CF3C6H4
Br
Br
Br
Br
Cl
Cl
Cl
3
3
9
24
5
6
4a
5a
5b
5c
5d
5e
5f
Complex mixture
C2H5
C2H5
C2H5
C2H5
C2H5
C2H5
41
31
13
48
50
8
3
tellurapyranes 6e and 6f were obtained in 8% and
7% yields, respectively, in both cases as compara-
tively air-stable oily matters. All the physical and
spectral data of 6e and 6f, involving MS, infrared
(IR), 1H nuclear magnetic resonance (NMR), and
13C NMR spectra, as well as the elemental analy-
sis data, were fully consistent with the structure of
the [4+2] cycloadducts of the in situ generated tel-
lurobenzaldehydes B. However, all attempts for the
improvement of the yields of 6e and 6f by modi-
fying the reaction procedure and conditions were
not successful at all. All results on the attempts
for generation and trapping of tellurobenzaldehy-
des B using 2,3-dimethyl-1,3-butadiene are shown in
Table 2.
Reaction of Bis(N,N-dialkylcarbamoyltelluro)-
arylmethanes (4, 5) with SnCl4 in the Absence of
Trapping Agents
We already reported that the reaction of bis(N,N-
diethylcarbamoylseleno)methanes with SnCl4 in
the absence of trapping agents afforded β-1,3,5-
triselenananes, the trimeric products of selenoalde-
hydes, in moderate-to-high yields [19,20]. However,
in spite of the exhaustive efforts, reaction of 5a–5d
with SnCl4 only afforded a complex mixture con-
taining the corresponding benzaldehydes and a trace
amount of stilbene derivatives 7 along with the extru-
sion of elemental tellurium, and 1,3,5-tritelluranes
were not obtained at all in contrast with the cases of
TABLE 2 Generation and Trapping of Telluroaldehydes B through the Reaction of Bis(N,N-diethylcarbamoyltelluro)methanes
5 with SnCl4 in the Presence of 2,3-Dimethyl-1,3-butadiene
Substrate
Yield (%)
6
R
5
Lewis Acid (mol)
Solvent
Temp (◦C)
Time (h)
C6H5
C6H5
C6H5
m-ClC6H4
H
Mes
p-FC6H4
p-CF3C6H4
5a
5a
5a
5b
5c
5d
5e
5f
BF3·OEt2 (2.0)
SnCl4 (2.0)
SnCl4 (2.0)
SnCl4 (2.0)
SnCl4 (2.0)
SnCl4 (2.0)
SnCl4 (2.0)
SnCl4 (2.0)
CH2Cl2
CH2Cl2
0
0
1
1
1
3
2
1
4
2
Complex mixture
Complex mixture
Complex mixture
Complex mixture
Complex mixture
Complex mixturea
8
Benzene
Benzene
Benzene
Benzene
Benzene
Benzene
R.T.
R.T.
R.T.
R.T.
R.T.
R.T.
7
aUncharacterized oligomeric products containing Sn and Te atoms were mainly obtained.
Heteroatom Chemistry DOI 10.1002/hc

SnCl4-Induced Unsymmetrical Cleavage of Bis(N,N-diethylcarbamoyltelluro)arylmethanes 485
SCHEME
2 Plausible pathway for the generation of tellurobenzaldehydes B through the reaction of bis(N,N-
diethylcarbamoyltelluro)arylmethanes 5 with SnCl4.
the reaction starting from the selenium analogues.
However, when 5a (R2 = C6H5) was treated with
SnCl4 (1.5 mol) in CDCl3 in an NMR tube and
the reaction was monitored by using 1H NMR at
298 K, a characteristic singlet signal at δ = 5.23
[19, 20], assignable to the methine proton of sym-
metrical β-1,3,5-tritellurane 8a, was observed in the
NMR spectrum of the reaction mixture. Further-
more, along with standing of the reaction mixture,
a new singlet signal at δ = 9.70, assigned to the
formyl proton of benzaldehyde, was gradually in-
creasing along with the extrusion of elemental tel-
lurium. These results suggested the in situ forma-
tion of β-1,3,5-tritellurane D through trimerization
of intermediary tellurobenzaldehude B as well as the
subsequent oxidative decomposition of D to form
aldehydes.
mer results suggested the in situ generation of in-
termediary telluronium ions E, which would un-
dergo Friedel–Crafts type reaction with benzene to
form 9e [28–35] via intermediary F. The formation
of 10 was also explained by the nucleophilic attack
of allyltrimethylsilane to the tellurium atom of sub-
strates 5. Therefore, a plausible formation mech-
anism of telluroaldehydes B involving an in situ
generation of telluronium ions E through an SnCl4-
induced unsymmetrical cleavage of substrates 5, as
shown in Scheme 2, is proposed. However, all at-
tempts for trapping of intermediates E were not
successful.
CONCLUSION
In addition, treatment of 5e (R2 = p-FC6H4) with
SnCl4 (1.5 mol) in benzene at R.T. afforded an un-
expected triarylmethane 9e (R2 = p-FC6H4) [21–27]
in 12% yield besides a complex mixture. Further-
more, the similar reaction of 5e with SnCl4 carried
out in CH2Cl2 in the presence of an excess amount
of allyltrimethylsilane at –78◦C afforded unstable Te-
allyl N,N-diethyltellurocarbamate (10) in 12% yield
besides several uncharacterized products. The for-
In conclusion, we attempted the SnCl4-induced
unsymmetrical
cleavage
of
bis(N,N-diethyl-
carbamoyltelluro)arylmethanes 5, and trapping of
tellurobenzaldehydes were only achieved in the case
starting from 5 bearing an electron-withdrawing
group on the aryl moiety. Further inspection for
the reaction pathway to form telluroaldehydes A,
as well as the further improvement of the reaction
conditions, are under way in our laboratory.
Heteroatom Chemistry DOI 10.1002/hc

486 Shimada et al.
EXPERIMENTAL
Instruments
Nacalai Tesque, Kyoto, Japan) were commercially
available reagent grade, and were used without any
pretreatment.
The melting points were determined with a Bu¨chi
535 micromelting-point apparatus. 1H NMR spectra
were recorded on a Bruker AC-400P (400 MHz) spec-
trometer (Bruker Biospin, Karlsruhe, Germany),
and the chemical shifts of the 1H NMR spectra
are given in δ relative to internal tetramethylsi-
lane. 13C NMR spectra were recorded on a Bruker
AC-400P (101 MHz; Bruker Biospin). Mass spectra
were recorded on a Hitachi M-2000 mass spectrome-
ter (Hitachi High-Technologies, Tokyo, Japan) with
electron-impact ionization at 20 or 70 eV using a di-
rect inlet system. IR spectra were recorded for thin
film (neat) or KBr disks on a JASCO FT/IR-7300 spec-
trometer (JASCO, Tokyo, Japan). Elemental analyses
were performed using a Yanagimoto CHN corder
MT-5 (Yanaco, Kyoto, Japan).
Preparation of Bis(N,N-dialkylcarbamoyl)
Ditellurides (1, 2)
Bis(N,N-dimethylcarbamoyl) ditelluride (1) was pre-
pared according to our previous report [8]. DEF
(20 mL) was treated with lithium (347 mg, 50.0
mmol) and elemental tellurium (1.29 g, 10.1 mmol)
at 110◦C for 20 h, and then oxygen gas was bub-
bled into the reaction mixture at 0◦C for 1.5 h.
The reaction was quenched with a small amount
of water. The reaction mixture was extracted with
chloroform, and the organic layer was dried over
anhydrous Na2SO4 powder. After removal of the
solvent in vacuo, crude bis(N,N-diethylcarbamoyl)
ditelluride (2, 610 mg, 27% yield) was obtained as
a black oil. However, chromatographic purification
of 2 was unsuccessful due to the facile decomposion
through the contact with silica gel.
Materials
Column chromatography was performed using silica
gel (Merck, Cat. No. 7734 or 9385, Merck, Darm-
stadt, Germany) without a pretreatment. CH2Cl2
(Kanto Chemical, Tokyo, Japan) and CHCl3 (Kanto
Chemical) were dried over P4O10 (Kanto Chemi-
cal), and were freshly distilled before use. Hex-
ane (Kanto Chemical), benzene (Kanto Chemical),
DMF (Kanto Chemical), and DEF (Tokyo Chem-
ical Industry, Tokyo, Japan) were dried over cal-
cium hydride (CaH2, Kanto Chemical) and freshly
distilled before use. Ethanol (Wako Pure Chemi-
cal Industries, Tokyo, Japan) was dried over anhy-
drous magnesium sulfate (MgSO4, Kanto Chemical),
and were freshly distilled before use. All of the sub-
strates and reagents, including elemental tellurium
(Wako Pure Chemical Industries), benzal bromide,
(Wako Pure Chemical Industries), m-chlorobenzal
bromide (Wako Pure Chemical Industries), p-
fluorobenzal chloride (Wako Pure Chemical Indus-
tries), p-trifluoromethylbenzal chloride (Wako Pure
Chemical Industries), dibromomethane (Wako Pure
Chemical Industries), 2,4,6-trimethylbenzaldehyde
(Wako Pure Chemical Industries), 2,3-dimethyl-1,3-
butadiene (Wako Pure Chemical Industries), al-
lyltrimethylsilane (Wako Pure Chemical Industries),
boron trifluoride diethyl ether complex (BF3·OEt2,
Wako Pure Chemical Industries), stannic chloride
(SnCl4, Wako Pure Chemical Industries), lithium
metal (Wako Pure Chemical Industries), sodium
metal (Wako Pure Chemical Industries), sodium
borohydride (NaBH4, Wako Pure Chemical Indus-
tries), anhydrous sodium sulfate powder (Na2SO4,
Kanto Chemical), and molecular sieves 4A (MS-4A,
1 (R1 = CH3) [8]: Yellow needles, melting point
(mp) 121.0–122.0◦C; MS (m/z) 404 (M+; 0.4%, 130Te);
IR (KBr) 2908, 1657, 1399, 1350, 1248, 1074, 870
1
cm−1; H NMR (CDCl3) δ = 3.08 (6H, s), 3.11 (6H,
s); 13C NMR (CDCl3) δ = 36.2 (q), 40.7 (q), 145.6 (s).
Calcd for C6H12N2O2Te2: C, 18.04; H, 3.03; N, 7.01.
Found: C, 18.06; H, 2.95; N, 7.03.
2 (R1 = C2H5): Black oil; MS (m/z) 456 (M+;
0.3%, 130Te), 100 (Et2NCO; bp); IR (neat) 2987, 1693,
1471, 1301, 1205, 1067, 828 cm−1; 1H NMR (CDCl3)
δ = 1.11–1.32 (12H, m), 3.42–3.51 (8H, m).
A Typical Procedure for the One-Pot Synthesis of
Bis(N,N-dialkylcarbamoyltelluro)arylmethanes (4, 5)
from DMF and DEF. A 50 mL DEF was treated with
lithium metal (1.402 g, 202 mmol) and elemental
tellurium (5.117 g, 40.1 mmol) under 110◦C for 2 h
under an Argon atmosphere. After cooling the reac-
tion mixture to 0◦C, the reaction mixture was treated
with a substituted benzal halide 3 (33.0 mmol) under
R.T. for 3 h. The reaction was quenched by the addi-
tion of water, and the reaction mixture was extracted
with hexane–dichloromethane (3:1), and the organic
layer was dried over anhydrous Na2SO4. After re-
moving the solvents in vacuo, the residual crude
mixture was subjected to column chromatographic
separation on silica gel to afford the correspond-
ing bis(N,N-diethylcarbamoyltelluro)arylmethanes
(5) as a yellow-to-brown powder or oil.
5a (R1 = C2H5, R2 = C6H5): Pale yellow powder,
mp 93.5–95.0◦C (decomposion); MS (FAB+, m/z) 547
(M++1; 0.3%, 128Te); 544 (M+; 0.3%, 128Te, 126Te),
448 (M+-CONEt2; 2%, 130Te, 128Te), 100 (CONEt2;
Heteroatom Chemistry DOI 10.1002/hc

SnCl4-Induced Unsymmetrical Cleavage of Bis(N,N-diethylcarbamoyltelluro)arylmethanes 487
(FC6H4CHTe; 10%, 126Te), 100 (Et2NCO; bp), 72
(Et2N; 8%); IR (KBr) 2976, 2933, 1666, 1603, 1503,
1460, 1399, 1301, 1214, 1102, 837, 757, 649 cm−1; 1H
NMR (CDCl3) δ = 1.17 (6H, t, J = 7.1 Hz), 1.18 (6H,
t, J = 7.1 Hz), 3.077 (2H, q, J = 7.1 Hz), 3.078 (2H,
q, J = 7.1 Hz), 3.44–3.58 (4H, m), 5.90 (1H, s), 6.84
(2H, t, J = 8.7 Hz), 7.46 (2H, dd, J = 8.7, 5.4 Hz);
13C NMR (CDCl3) δ = –6.2 (d), 13.4 (q), 14.5 (q), 41.4
(t), 44.3 (t), 114.5 (dd, JC–F = 21.8 Hz), 129.4 (dd,
JC–F = 8.6 Hz), 145.8 (d, JC–F = 2.9 Hz), 158.8 (s),
161.1 (d, JC–F = 245.4 Hz). HRMS (EI+, m/z): Calcd
for C17H25FN2O2Te2: 565.0062. Found: 565.0060.
5f (R1 = C2H5, R2 = p-CF3C6H4): Yellow oil; MS
(m/z) 618 (M+; 1%, 130Te), 616 (M+; 4%, 130Te, 128Te),
614 (M+; 3%, 128Te), 460 (M+-(C2H5)2NCO; 3%,
130Te), 458 (M+-(C2H5)2NCO; 6%, 130Te, 128Te), 456
(M+-(C2H5)2NCO; 4%, 128Te), 330 (p-CF3C6H4CHTe;
bp, 130Te), 328 (p-CF3C6H4CHTe; 99%, 128Te); IR
(neat) 2973, 2855, 1634, 1611, 1400, 1323, 1244,
1212, 1163, 1108, 1066, 835 cm−1; 1H NMR (CDCl3)
δ = 1.15–1.22 (12H, m), 3.09 (4H, br.q, J = 7.0 Hz),
3.40–3.60 (4H, m), 5.85 (1H, s), 7.41 (2H, br.d, J =
8.0 Hz), 7.60 (2H, br.d, J = 8.0 Hz); 13C NMR (CDCl3)
δ = –6.0 (d), 13.3 (q), 14.5 (q), 41.5 (t), 44.4 (t),
124.0 (q, JC–F = 240.0 Hz), 124.8 (br.d), 128.2 (d),
154.1 (s), 158.6 (s). HRMS (EI+, m/z): Calcd for
C18H25F3N2O2Te2: 617.9993. Found: 617.9995.
bp); IR (KBr) 2973, 1636, 1452, 1399, 1297, 1244,
1
1209, 1105, 1071, 832, 646 cm−1; H NMR (CDCl3)
δ = 1.17 (6H, t, J = 7.1 Hz), 1.18 (6H, t, J = 7.1 Hz),
3.08 (2H, q, J = 7.1 Hz), 3.09 (2H, q, J = 7.1 Hz), 3.49
(2H, dq, J = 13.9, 7.1 Hz), 3.53 (2H, dq, J = 13.9,
7.1 Hz), 5.93 (1H, s), 7.02–7.49 (5H, m); 13C NMR
(CDCl3) δ = –4.4 (d), 13.4 (q), 14.5 (q), 41.4 (t), 44.4
(t), 126.3 (d), 127.9 (d), 128.0 (d), 149.8 (s), 159.0 (s).
Calcd for C17H26N2O2Te2: C, 37.42; H, 4.80; N, 5.13.
Found: C, 37.19; H, 4.66; N, 5.05.
5b (R1 = C2H5, R2 = m-ClC6H4): Black oil; MS
(FAB+, m/z) 583 (M++1; 22%, 130Te, 128Te), 581 (M+;
22%, 128Te), 100 (CONEt2; bp); IR (neat) 2978, 1662,
1466, 1396, 1300, 1246, 1208, 1111, 834, 784, 694,
648 cm−1
;
1H NMR (CDCl3) δ = 1.18 (6H, t, J =
7.1 Hz), 1.19 (6H, t, J = 7.1 Hz), 3.07 (2H, q, J =
7.1 Hz), 3.08 (2H, q, J = 7.1 Hz), 3.48 (2H, dq, J =
13.8, 7.1 Hz), 3.54 (2H, dq, J = 13.8, 7.1 Hz), 5.85 (1H,
s), 7.01–7.48 (4H, m); 13C NMR (CDCl3) δ = –6.2 (d),
13.2 (q), 14.3 (q), 41.3 (t), 44.1 (t), 125.9 (d), 126.1
(d), 127.8 (d), 128.8 (d), 132.9 (s), 151.7 (s), 158.3
(s). HRMS (FAB+) Calcd for C17H26ClN2O2Te2: m/z
582.9780. Found: m/z 582.9778.
5c (R1 = C2H5, R2 = H): Yellow oil; MS (EI+, m/z)
470 (M+; 21%, 128Te), 468 (M+; 13%, 128Te, 126Te),
330 (M+-2NEt2; 29%, 130Te), 328 (M+-2NEt2; 29%,
130Te, 128Te), 100 (CONEt2; bp), 72 (Et2N; 25%); IR
(neat) 2974, 1644, 1399, 1244, 1097, 836 cm−1; H
1
NMR (CDCl3) δ = 1.18 (6H, t, J = 7.1 Hz), 1.23 (6H,
t, J = 7.1 Hz), 3.12 (4H, q, J = 7.1 Hz), 3.51 (4H,
q, J = 7.1 Hz), 3.91 (2H, s); 13C NMR (CDCl3) δ =
–31.0 (t), 13.3 (q), 14.4 (q), 41.3 (t), 44.3 (t), 157.1 (s).
Calcd for C11H22N2O2Te2: C, 28.14; H, 4.72; N, 5.97.
Found: C, 27.69; H, 4.50; N, 5.89.
A
Typical Procedure for the Treatment of
Bis(N,N-dialkylcarbamoyltelluro)arylmethanes (4,
5) with SnCl4 in the Presence of 2,3-Dimethyl-1,3-
Butadiene. A 10 mL benzene solution of bis(N,N-
diethylcarbamoyltelluro)-4-fluorophenylmethane
(5e, 564 mg, 1.00 mmol) was treated with SnCl4
(1M benzene solution, 2.00 mL, 2.00 mmol, 2.0o
mol) in the presence of an excess amount of 2,3-
dimethyl-1,3-butadiene (821 mg, 10.0 mol) under
R.T. for 4 h, and the reaction mixture was quenched
by the addition of saturated NaHCO3 solution. The
reaction mixture was extracted with chloroform,
and the organic layer was dried over anhydrous
Na2SO4. After removing the solvent in vacuo, the
residual crude mixture was subjected to column
chromatographic separation on silica gel to afford
the [4+2] cycloadduct 6e (25 mg, 8% yield) as
yellow oil.
5d (R1 = C2H5, R2 = Mes): Pale brown solid,
mp 105.0–106.0◦C (decomposition); MS (FAB+,
m/z) 589 (M++1; 2%, 128Te), 587 (M+; 2%, 128Te,
126Te), 488 (M+-CONEt2; 6%, 128Te), 486 (M+-
CONEt2; 6%, 128Te, 126Te), 362 (M+-TeCONEt2; 42%,
128Te), 360 (M+-TeCONEt2; 40%, 128Te, 126Te), 261
(MesCHTe+1; 10%, 128Te), 259 (MesCHTe+1; 10%
126Te), 100 (CONEt2; bp), 72 (Et2N; 38%); IR (KBr)
1
2975, 1653, 1467, 1380, 1243, 1107, 835 cm−1; H
NMR (CDCl3) δ = 1.12–1.19 (12H, m), 2.24 (3H, s),
2.48 (3H, s), 2.66 (3H, s), 3.05 (4H, q, J = 6.9 Hz),
3.48–3.50 (4H, m), 6.57 (1H, s), 6.77 (1H, s), 6.81
(1H, s); 13C NMR (CDCl3) δ = –6.4 (d), 13.4 (q), 14.5
(q), 20.7 (q), 21.0 (q), 23.2 (q), 41.3 (t), 43.8 (t), 128.7
(d), 129.6 (d), 133.9 (s), 135.7 (s), 136.7 (s), 140.4
(s), 157.2 (s). Calcd for C20H32N2O2Te2: C, 40.87; H,
5.49; N, 4.77. Found: C, 40.48; H, 5.32; N, 4.71.
5e (R1 = C2H5, R2 = p-FC6H4): Pale yellow
powder, mp 61.0–63.2◦C (decomposition); MS (EI+,
m/z) 564 (M+, 0.04%, 128Te), 562 (M+; 0.03%,
128Te, 126Te), 236 (FC6H4CHTe; 17%, 128Te), 234
6e (R2 = p-FC6H4): Yellow oil; MS (m/z) 320
(M+: 19%, 130Te), 318 (M+; 10%, 128Te), 238 (p-
FC6H4CHTe; 18%, 130Te), 236 (p-FC6H4CHTe; 20%,
128Te), 189 (bp); IR (neat) 2856, 2345, 1601, 1507,
1447, 1375, 1227, 1155, 832, 732 cm−1 1H NMR
;
(CDCl3) δ = 1.84 (3H, s), 1.87 (3H, s), 2.46 (1H, dd, J =
13.8, 3.6 Hz), 2.96 (1H, dd, J = 13.8, 11.6 Hz), 3.16
(1H, d, J = 11.9 Hz), 3.81 (1H, br.d, J = 11.9 Hz),
Heteroatom Chemistry DOI 10.1002/hc

488 Shimada et al.
4.86 (1H, dd, J = 11.6, 3.6 Hz), 6.94 (2H, br.t, J =
8.8 Hz), 7.35 (2H, br.dd, J = 8.8, 5.4 Hz); 13C NMR
(CDCl3) δ = 4.4 (dd), 18.2 (q), 20.4 (q), 33.7 (br.s),
silane (571 mg, 5.00 mmol, 5.00 mol) under –78◦C
for 4 h, and the reaction mixture was quenched by
the addition of saturated NaHCO3 solution. The
reaction mixture was extracted with chloroform,
and the organic layer was dried over anhydrous
Na2SO4. After removing the solvent in vacuo, the
residual crude mixture was subjected to column
chromatographic separation on silica gel to afford
Te-allyl N,N-diethyltellurocarbamate 10e (33 mg,
12% yield) as unstable yellow oil. The structure
of compound 10e was confirmed by independent
synthesis through the reaction of in situ generated
N,N-diethyltellurocarbamate ion with ally bromide
through a similar method shown above.
43.0 (dd), 115.2 (dd, JC–F = 21.8 Hz), 129.2 (dd, JC–F
=
7.2 Hz), 129.8 (s), 132.2 (s), 141.3 (d, JC–F = 4.6 Hz),
161.2 (d, JC–F = 243.6 Hz). HRMS (EI+; m/z) Calcd
for C13H15FTe: 318.0203. Found: 328.0208.
6f (R2 = p-CF3C6H4): Yellow oil; MS (m/z) 370
(M+; 8%, 130Te), 368 (M+; 12%, 128Te), 288 (p-
CF3C6H4CHTe; 16%, 130Te), 286 (p-CF3C6H4CHTe;
14%, 128Te), 239 (bp); IR (neat) 3010, 2860, 1324,
1
1165, 1127, 1068 cm−1; H NMR (CDCl3) δ = 1.84
(3H, br.s), 1.89 (3H, br.s), 2.50 (1H, dd, J = 13.5,
3.5 Hz), 2.95–3.05 (1H, dd, J = 13.5, 10.5 Hz), 3.19
(1H, br.d, J = 12.0 Hz), 3.87 (1H, br.d, J = 12.0 Hz),
4.91 (1H, d, J = 10.5, 3.5 Hz), 7.47 (2H, br.d, J =
8.7 Hz), 7.50 (2H, br.d, J = 8.7 Hz); 13C NMR (CDCl3)
δ = 4.7 (d), 18.3 (q), 20.4 (q), 33.8 (t), 42.2 (dd), 124.5
(q, JC–F = 210.6 Hz), 126.3 (br.d), 128.0 (d), 130.0
(s), 132.1 (s), 149.9 (s). HRMS (EI+; m/z) Calcd for
C14H15F3Te: 370.0188. Found: 370.0192.
10 (R1 = C2H5): Yellow oil, 1H NMR (CDCl3) δ =
1.15 (3H, t, J = 7.1 Hz), 1.22 (3H, t, J = 7.1 Hz), 3.15
(2H, q, J = 7.1 Hz), 3.48 (2H, q, J = 7.1 Hz), 3.68
(2H, d, J = 8.0 Hz), 4.84 (1H, br.d, J = 9.8 Hz), 5.09
(1H, br.d, J = 17.0 Hz), 6.09 (1H, ddt, J = 17.0, 9.8,
8.0 Hz).
Treatment of Bis(N,N-dialkylcarbamoyltelluro)-
arylmethane 5e with SnCl4 in the Absence of Trapping
Agents. A 10 mL benzene solution of bis(N,N-
diethylcarbamoyltelluro)-p-fluorophenylmethane
(5e, 2.64 g, 4.68 mmol) was treated with SnCl4
(1M benzene solution 18.7 mL, 18.7 mmol, 4.00
mol) under R.T. for 3 h, and the reaction mix-
ture was quenched by the addition of saturated
NaHCO3 solution. The reaction mixture was ex-
tracted with chloroform, and the organic layer
was dried over anhydrous Na2SO4. After removing
the solvent in vacuo, the residual crude complex
mixture was subjected to column chromatographic
separation on silica gel to afford 1,1-diphenyl-1-
p-fluorophenylmethane 9e (98 mg, 8% yield) as
colorless needles.
REFERENCES
[1] Guziec, L. J.; Guziec, F. S., Jr. Comprehensive
Organic Functional Group Transformations II; Ka-
tritzky, A. R.; Taylor, R. J. K. (Eds.); Elsevier: Oxford,
UK, 2005; 3, 397–417.
[2] Kuhn, N.; Verani, G. Handbook of Chalcogen Chem-
istry; Devillanova, F. A. (Ed.); Royal Society of Chem-
istry: London, 2007; 107–144.
[3] Ogawa, A.; Sonoda, N. Handbook of Reagents for Or-
ganic Synthesis: Reagents for Silicon-Mediated Or-
ganic Synthesis; Fuchs, P. L. (Ed.); Wiley: Chichester,
UK 2011; 82–83.
[4] Murai, T. Organoselenium Chemistry; Wirth, T.
(Ed.); Wiley–VCH: Weinheim, Germany, 2012; 257–
285.
[5] Erker, G.; Hock, R. Angew Chem 1989, 101, 181–182.
[6] Segi, M.; Koyama, T.; Takata, Y.; Nakajima, T.; Suga,
S. J Am Chem Soc 1989, 111, 8749–8751.
[7] Fischer, H.; Frueh, A.; Troll, C. J Organomet Chem
1991, 415, 211–221.
[8] Shimada, K.; Oikawa, S.; Nakamura, H.; Takikawa,
Y. Chem Lett 1995, 135–136.
[9] Shimada, K.; Oikawa, S.; Takikawa, Y. Chem Lett
1992, 1389–1392.
[10] Inoue, T.; Mogami, T.; Kambe, N.; Ogawa, A.; Son-
oda, N. Heteroat Chem 1993, 4, 471–474.
[11] Ibi, K.; Imase, T.; Kato, S.; Ando, F.; Koketsu, J. Z
Anorg Allg Chem 2007, 633, 635–639.
9e (R2 = p-FC6H4) [21]: Colorless needles, mp
58.7–59.5◦C (lit. 62.0–63.0◦C); MS (m/z) 262 (M+;
bp), 185 (M+-C6H5; 71%), 165 (M+-ArH; 48%); IR
(KBr) 3024, 1598, 1501, 1445, 1227, 1156, 1086,
1024, 806, 742 cm−1; 1H NMR (CDCl3) δ = 5.52 (1H,
s), 6.96–7.30 (14H, m); 13C NMR (CDCl3) δ = 56.0
(d), 115.1 (dd, JC–F = 21.8 Hz), 126.4 (d), 128.4 (d),
129.3 (d), 130.8 (dd, JC–F = 8.7 Hz), 139.6 (s), 143.7
(s), 161.4 (d, JC–F = 243.6 Hz).
[12] Shimada, K.; Gong, Y.; Nakamura, H.; Matsumoto,
R.; Aoyagi, S.; Takikawa, Y. Tetrahedron Lett 2005,
46, 3775–3778.
[13] Gong, Y.; Shimada, K.; Nakamura, H.; Fujiyama, M.;
Kodama, A.; Otsuki, M.; Matsumoto, R.; Aoyagi, S.;
Takikawa, Y. Heteroat Chem 2006, 17, 125–135.
[14] Zingaro, R. A.; Herrera, C.; Meyers, E. A. J Organomet
Chem 1986, 306, C36–C40.
Treatment of Bis(N,N-diethylcarbamoyltelluro)-
arylmethane 5e with SnCl4 in the Presence
of Allyltrimethylsilane. A 10 mL CH2Cl2 so-
lution
of
bis(N,N-diethylcarbamoyltelluro)-p-
fluorophenylmethane (5e, 564 mg, 1.00 mmol) was
treated with SnCl4 (1M CH2Cl2 solution, 4.0 ml, 4.00
mmol, 4.00 mol) in the presence of allyltrimethyl-
[15] Suzuki, H.; Manabe, H.; Kawaguchi, T.; Inouye, M.
Bull Chem Soc Jpn 1987, 60, 771–772.
Heteroatom Chemistry DOI 10.1002/hc

SnCl4-Induced Unsymmetrical Cleavage of Bis(N,N-diethylcarbamoyltelluro)arylmethanes 489
[16] Zingaro, R. A.; Herrera, C. Bull Chem Soc Jpn 1989,
[25] Andrews, A. F.; Mackie, R. K.; Walton, J. C. J Chem
Soc Perkin Trans 1980, 2, 96–102.
62, 1382–1384.
[17] Shimada, K.; Oikawa, S.; Nakamura, H.; Moro-oka,
A.; Kikuchi, M.; Maruyama, A.; Suzuki, T.; Kogawa,
H.; Inoue, Y.; Gong, Y.; Aoyagi, S.; Takikawa, Y. Bull
Chem Soc Jpn 2005, 78, 899–905.
[18] Shimada, K.; Moro-oka, A.; Maruyama, A.; Fujisawa,
H.; Saito, T.; Kawamura, R.; Kogawa, H.; Sakuraba,
M.; Takata, Y.; Aoyagi, S.; Takikawa, Y.; Kabuto, C.
Bull Chem Soc Jpn 2007, 80, 567–577.
[26] Prakash, G. K. S.; Panja, C.; Shakhmin, A.; Shah, E.;
Mathew, T.; Olah, G. A. J Org Chem 2009, 74, 8659–
8668.
[27] Zhang, J.; Bellomo, A.; Creamer, A. D.; Dreher, S. D.;
Walsh, P. J. J Am Chem Soc 2012, 134, 13765–13772.
[28] Renard, M.; Hevesi, L. Tetrahedron Lett 1983, 24,
3911–3912.
[29] Silveira, C. C.; Comasseto, J. V.; Catani, V. Synth
Commun 1985, 15, 931–937.
[30] Hevesi, L. Phosphorus Sulfur Relat Elem 1988, 38,
191–200.
[19] Takikawa, Y.; Uwano, A.; Watanabe, H.; Asanuma,
M.; Shimada, K. Tetrahedron Lett 1989, 30, 6047–
6050.
[20] Shimada, K.; Okuse, S.; Takikawa, Y. Bull Chem Soc
Jpn 1992, 65, 2848–2850.
[21] Dayal, S. K.; Ehrenson, S.; Taft, R. W. J Am Chem
Soc 1972, 94, 9113–9122.
[31] Hevesi, L.; Lavoix, A. Tetrahedron Lett 1989, 30,
4433–4434.
[32] Hermans, B.; Hevesi, L. Tetrahedron Lett 1990, 31,
4363–4366.
[22] Nesmeyanov, A. N.; Kravtsov, D. N.; Kvasov, B. A.;
Pombrik, S. I.; Fedin, E. I. J Organomet Chem 1973,
47, 367–374.
[23] Yolles, S.; Woodland, J. H. R. J Organomet Chem
1973, 54, 95–104.
[33] Silveira, C. C.; Lenarda˜o, E. J.; Comasseto, J. V.;
Dabdoub, M. J. Tetrahedron Lett 1991, 32, 5741–
5744.
[34] Hevesi, L. Phosphorus, Sulfur Silicon Relat Elem
2001, 171–172, 57–72.
[24] Shutske, G. M. J Org Chem 1977, 42, 374–376.
[35] Podder, S.; Roy, S. Tetrahedron 2007, 63, 9146–9152.
Heteroatom Chemistry DOI 10.1002/hc