Synthetic utility of 1,1,2,2-tetraaryIdisilanes: Radical reduction of alkyl phenyl chalcogenides

Article abstract of DOI:10.1039/a905937g

Reactivity of tetraaryldisilanes as radical reducing agents of alkyl phenyl chalcogenides initiated by Et3B or AIBN was studied. Here, the reactivity of alkyl sulfide was poor; however, various alkyl phenyl selenides and tellurides were reduced to the corresponding hydrocarbons in good yields with 1,1,2,2-tetraphenyldisilane. The Royal Society of Chemistry 1999.

Full text of DOI:10.1039/a905937g

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Synthetic utility of 1,1,2,2-tetraaryldisilanes: radical reduction of
alkyl phenyl chalcogenides
Osamu Yamazaki,a Hideo Togo*ab and Masataka Yokoyamaab
a Graduate School of Science and Technology, b Department of Chemistry, Faculty of Science,
Chiba University, Yayoi-cho 1-33, Inageku, Chiba 263-8522, Japan
Received (in Cambridge, UK) 22nd July 1999, Accepted 26th August 1999
Reactivity of tetraaryldisilanes as radical reducing agents of alkyl phenyl chalcogenides initiated by Et3B or AIBN
was studied. Here, the reactivity of alkyl sulfide was poor; however, various alkyl phenyl selenides and tellurides were
reduced to the corresponding hydrocarbons in good yields with 1,1,2,2-tetraphenyldisilane.
Table 1 Radical reduction of 3-cholestanyl phenyl chalcogenides to
cholestane with Ph4Si2H2
Introduction
The major approach to organic synthesis with free radical reac-
tions usually deals with tributyltin hydride.1 However, it is well
known that there are several problems incurred in the tributyl-
tin hydride method such as toxicity and disposal, work-up and
complete removal of the tin species from the products. There-
fore, other radical reagents have been required in place of
tin compounds. Recently, organosilanes such as (Me3Si)3SiH
and Ph2SiH2 have been utilized in a wide variety of radical
reactions.2,3,4 We also reported radical reactions mediated by
water-soluble organosilanes in aqueous media.5 Generally, it is
recognized that organosilanes are shown to be highly efficient
and superior radical reagents compared with organotin com-
pounds from the ecological and practical viewpoints. Recently,
we have reported the utilization of tetraaryldisilanes, which are
air-stable crystals, for three types of radical reactions with alkyl
bromides such as reduction, reductive addition to olefins, and
alkylation onto heteroaromatic bases.6 Here, the utilization
of tetraaryldisilanes 1 as a radical reducing agent with alkyl
phenyl chalcogenides is demonstrated. Usually, sugar chalco-
genides are much more stable than sugar halides for storage and
chemical treatment. Therefore, it would be very convenient if
the radical reaction of chalcogenides with tetraaryldisilanes
would work effectively.
Entry 3-Chol-XPh
Initiator
Yielda (%)
1
2
Et3B
AIBN
20 (79)
32 (65)
3
4
5
6
7
Et3B
99 (0)
87 (5)
9 (91)
trace (83)
trace (89)
AIBN
Et3Bb
Et3Bc
AIBNc
8
9
Et3B
AIBN
85 (3)
82 (5)
a Yield of recovered 3-cholestanyl phenyl chalcogenide is shown in
parentheses. b Ph2SiH2 was used instead of Ph4Si2H2. c Reaction was
carried out without Ph4Si2H2.
(Ph4Si2H2, 0.45 mmol) in ethyl acetate (3 ml) at room temper-
ature. After being stirred for 1 h, cholestane was obtained in
99% yield. In another method, Chol-SePh (0.3 mmol), Ph4Si2H2
(0.33 mmol), and AIBN (0.15 mmol) in ethyl acetate (3 ml) were
stirred under reflux conditions, and 0.15 mmol of AIBN was
added after 4 h, 20 h, 27 h and 49 h (total 0.75 mmol). After
65 h, the reaction mixture was evaporated and purified to give
cholestane in 52% yield and the recovered Chol-SePh in 36%
yield, respectively. This result indicates that the additional
AIBN is less effective. However, when the solution of Chol-
SePh (0.3 mmol), Ph4Si2H2 (0.75 mmol), and AIBN (0.75
mmol) in ethyl acetate (3 ml) was refluxed for 12 h, cholestane
was obtained in 87% yield and Chol-SePh was recovered in only
5% yield. Thus, it is important to initiate the radical reduction
by excess AIBN, and the reduction of 3-cholestanyl phenyl sul-
fide 2 and telluride 4 was carried out under the same conditions.
The results are shown in Table 1.
Scheme 1 Reaction mechanism.
Results and discussion
At first, the relative reactivity of alkyl phenyl chalcogenides
was studied. Thus, 3-cholestanyl phenyl chalcogenides (sulfide,
selenide, and telluride) were prepared from the corresponding
bromides. Under aerobic conditions, triethylborane (Et3B, 0.15
mmol) was added to a solution of 3-cholestanyl phenyl selen-
ide 3 (Chol-SePh, 0.3 mmol) and 1,1,2,2-tetraphenyldisilane
The reduction of 3-cholestanyl phenyl sulfide to cholestane
initiated by Et3B or AIBN did not proceed effectively and the
starting sulfide was recovered mainly. However, 3-cholestanyl
phenyl selenide and 3-cholestanyl phenyl telluride were reduced
in good yields. Use of diphenylsilane instead of Ph4Si2H2 for
J. Chem. Soc., Perkin Trans. 1, 1999, 2891–2896
This journal is © The Royal Society of Chemistry 1999
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Table 2 Radical reduction of RSePh to RH
Table 3 Reactivities of organodisilanes 1a–1d
R-SePh
Initiator
Yield (%)
Et3B
AIBN
91
100
5
6
Et3B
AIBN
88
94
Disilane 1: Ar4Si2H2
Et3B
AIBN
91a
91a
7
8
Et3B
AIBN
96
23
Yields (%)
Entry
Disilane 1
Chol-TePh
Chol-H
Et3B
AIBN
26
85
9
1
2
3
4
1a
1b
1c
1d
3
2
4
85
95
88
24
59
Et3B
65
10
ethyl acetate. In contrast to sugar selenide 8, phenyl 2,3,5-tri-O-
benzyl-1-seleno--ribofuranoside 9 was reduced in good yield
by Ph4Si2H2 with AIBN at refluxing temperature in ethyl acet-
ate; however, in spite of the complete consumption of the start-
ing selenide, the reduction product was obtained in low yield
by Ph4Si2H2 with Et3B at room temperature. Probably, this low
reactivity is caused by the steric hindrance of the 2-O-benzyl
group, since phenyl 3,5-di-O-benzyl-2-deoxy-1-seleno--ribo-
furanoside 10 was reduced in moderate yield (65%) under Et3B
conditions. 2-Phenylselenosugars 11 and 12 were also reduced
to 2-deoxyglucosides in good yields under both Et3B and AIBN
conditions. Next, the radical reduction of the 2-phenylseleno-
adenosine derivative was carried out. The reduction products,
which were a mixture of a N-triphenylphosphinated compound
(major) and a dephosphinated compound (minor), were
obtained in moderate yields under both conditions.9 Thus, the
radical reduction of alkyl phenyl chalcogenides, especially alkyl
phenyl selenides, mediated by Ph4Si2H2 proceeded successfully
to give the corresponding reduction products in good yields.
The radical reactivity of other organodisilanes towards 3-
cholestanyl phenyl telluride was next investigated (Table 3). The
present tetraaryldisilanes were prepared by the dehydrogenative
coupling reaction of the corresponding diarylsilane in the pres-
ence of a Ti-complex.10 The radical reduction of 3-cholestanyl
phenyl telluride by organodisilane with Et3B showed good
reactivity for tetraaryldisilanes 1a–c; however, reactivity for 1,2-
dimethyl-1,2-diphenyldisilane 1d was low.
Among the tetraaryldisilanes 1a–c, 1,1,2,2-tetra(4-fluoro-
phenyl)disilane 1b was the most effective for the radical reduc-
tion. However, the use of organodisilane 1a is practically
recommended, since it is readily prepared in the best yield
among organodisilanes 1a–d.
Finally, in order to see the electronic effect of the aromatic
ring in the radical reduction of alkyl aryl selenides initiated by
Et3B or AIBN, the reactivities of 4-chlorophenyl tridecyl selen-
ide 14, phenyl tridecyl selenide 6, and 4-methoxyphenyl tridecyl
selenide 15 were compared, as shown in Table 4. However,
no remarkable difference in reactivity was observed among the
phenyl, 4-methoxyphenyl, and 4-chlorophenyl selenides.
The present radical reductions were carried out in ethyl
acetate from the environmental point of view. However, the
same treatment of alkyl phenyl selenides in benzene gave the
corresponding reduction products in good yields. Thus, radical
reduction of Chol-SePh in benzene initiated by AIBN gave
Et3B
AIBN
79
98
11
12
Et3B
AIBN
83
98
Et3B
AIBN
63b
57b
13
a A mixture of direct reduction product and 1,2-rearranged reduction
product. b A mixture of direct reduction product and N-deprotected
reduction product (-NH2).
the present radical reduction of Chol-SePh under Et3B condi-
tions resulted in a poor yield of cholestane. Furthermore, the
same radical reduction of Chol-SePh without Ph4Si2H2 was
carried out under both Et3B and AIBN conditions. However,
the starting Chol-SePh was recovered in high yields. Based on
these results, radical reduction of other alkyl phenyl selenides
with Ph4Si2H2 initiated by Et3B or AIBN was carried out, and
the results are shown in Table 2.
1-Adamantyl phenyl selenide 5, a tertiary alkyl group, and
phenyl 1-tridecyl selenide 6, a primary alkyl group, were also
reduced in high yields, respectively. Then, the radical reduc-
tion of various sugar selenides with Ph4Si2H2 was carried out.
Phenyl 2,3,4,6-tetra-O-acetyl-1-seleno-β--galactopyranoside 7
was reduced in high yields under Et3B and AIBN conditions,
respectively. Here, the reduction product contained a by-
product7 which was generated by the migration of the AcO
group from the 2-carbon to the 1-carbon via the anomer
radical, followed by hydrogen abstraction to give 1,3,4,6-tetra-
O-acetyl--galactose.8 Methyl 6-deoxy-6-phenylseleno--gluco-
pyranoside 8 was reduced in good yield by Ph4Si2H2 initiated by
Et3B at room temperature; however, this sugar selenide 8 was
reduced in low yield with AIBN under refluxing conditions.
Here, side reactions seem to occur at refluxing temperature in
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Table 4 Radical reduction of tridecyl aryl selenides with Ph4Si2H2
was extracted with CHCl3 and dried over Na2SO4. The solu-
tion was evaporated and the residue was purified by column
chromatography to give the selenide in 56% yield. Other selen-
ides and tellurides were prepared by the same procedure. Mp
55.0–56.0 ЊC; IR (KBr) 2930, 2850, 1580, 1480, 1460, 1445,
RSe-Ar
Initiator
Yield (%)
Et3B
AIBN
74
94
14
6
1435, 1380, 1070, 1020, 730, 690 cmϪ1 1H NMR (CDCl3)
;
δ = 0.58–2.01 (46H, m, cholestanyl), 3.19 (1H, tt, J = 12.4, 4.4
Hz, 3-CH), 7.24–7.28 (3H, m, ArH), 7.51–7.55 (2H, m, ArH);
MS (EI) Found: m/z 528.
Et3B
AIBN
88
94
3ꢀ-Cholestanyl phenyl telluride15 (4). 56% yield; oil; IR (Neat)
Et3B
AIBN
80
99
15
2930, 2850, 1580, 1470, 1445, 1435, 1380, 1020, 735, 690 cmϪ1
;
1H NMR (CDCl3) δ = 0.58–2.05 (46H, m, cholestanyl), 3.38
(1H, tt, J = 12.5, 4.6 Hz, 3-CH), 7.17–7.33 (3H, m, ArH), 7.75–
7.81 (2H, m, ArH); MS (EI) Found: m/z 578.
cholestane in 88% yield. An ethanol solvent was not effective
under the same treatment. Consequently, it is recommended
from the environmental point of view to carry out the radical
reaction with organodisilanes in ethyl acetate, instead of
benzene.
In conclusion, 1,1,2,2-tetraphenyldisilane is a useful reagent
for radical reduction of alkyl aryl selenides and tellurides, since
this organodisilane is a less toxic, air-stable, easily handled,
mild reagent compared to the known reducing reagents for
alkyl aryl selenides such as tin hydride,11 tris(trimethylsilyl)-
silane,3 Raney Ni, Li-EtNH2 and NiCl2ؒ6H2O–NaBH4.12
Furthermore, the reaction solvent, ethyl acetate, is environ-
mentally more benign than benzene and toluene.
Phenyl 1-tridecyl selenide (6). 97% yield; oil; IR (KBr) 2920,
1
2850, 1580, 1480, 1460, 1440, 1075, 1020, 730, 690 cmϪ1; H
NMR (CDCl3) δ = 0.88 (3H, t, J = 6.8 Hz, CH3-), 1.25 (18H, br
s, -CH2-), 1.39 (2H, br t, J = 7.3 Hz, -CH2-), 1.70 (2H, quintet,
J = 7.5 Hz, -CH2-), 2.91 (2H, t, J = 7.5 Hz, -CH2-), 7.21–7.28
(3H, m, ArH), 7.46–7.49 (2H, m, ArH); 13C NMR (CDCl3)
δ = 14.2(q), 22.8(t), 28.0(t), 29.2(t), 29.4(t), 29.6(t), 29.7(t),
29.7(t), 29.8(t), 29.9(t), 30.2(t), 32.0(t), 126.7(d), 129.0(d),
130.8(s), 132.4(d); MS (FABϩ) Found: m/z 340; Anal. Calcd
for C19H32Se: C, 67.23; H, 9.50%. Found: C, 67.23; H, 9.81%.
Phenyl 2,3,4,6-tetra-O-acetyl-1-seleno-ꢀ-D-galactopyranos-
ide16 (7). 93% yield; syrup; IR (Neat) 2980, 1750, 1580, 1370,
1230, 1050, 915, 745, 690 cmϪ1; 1H NMR (CDCl3) δ = 1.97 (3H,
s, -OAc), 2.04 (3H, s, -OAc), 2.08 (3H, s, -OAc), 2.10 (3H, s,
-OAc), 3.89–3.93 (1H, m, 5-CH), 4.10 (1H, dd, J = 11.4, 6.3 Hz,
6-CH), 4.17 (1H, dd, J = 11.4, 7.0 Hz, 6-CHЈ), 4.91 (1H, d,
J = 9.9 Hz, 1-CH), 5.02 (1H, dd, J = 9.9, 3.4 Hz, 3-CH), 5.27
(1H, t, J = 9.9 Hz, 2-CH), 5.42 (1H, dd, J = 3.4, 1.0 Hz, 4-CH),
7.28–7.37 (3H, m, ArH), 7.62–7.64 (2H, m, ArH); MS (FABϩ)
Found: m/z (M ϩ K) 527.
Experimental
General
1H NMR and 13C NMR spectra were obtained with JEOL-
JNM-GSX400, JEOL-JNM-LA-400 and JEOL-JNM-LA-500
spectrometers. Chemical shifts are expressed in ppm downfield
from TMS in δ units. Mass spectra were recorded in JEOL-HX-
110 and a JEOL-JMS-ATII15 spectrometers, and the source of
the K in the FAB MS is KI. IR spectra were measured with a
JASCO FT/IR-200 spectrometer. Microanalysis was performed
with a Perkin-Elmer 240 elemental analyser at the Chemical
Analysis Center of Chiba University. GC spectra were recorded
on a Shimadzu GC-8A gas chromatograph with a packed
column (OV-17 and SE-30). Melting points were determined on
a Yamato melting point apparatus Model MP-21. Wakogel
C-200 was used for column chromatography, and Wakogel
B-5F was used for PTLC. Column JAIGEL-1HF (CHCl3) and
JAIGEL-345-15 (CH3OH) were used for recycling preparative
HPLC (Japan Analytical Industry Co., HPLC-908). Solvents
were purified and dried by standard techniques. Disilanes 1a–1d
were prepared by the previously reported method.6,10
Methyl 6-deoxy-6-phenylseleno-ꢁ-D-glucopyranoside (8). 92%
yield; mp 68.5–70.5 ЊC; IR (KBr) 3370, 3200, 2930, 2900, 1580,
1435, 1190, 1150, 1115, 1040, 740, 695 cmϪ1; 1H NMR (CDCl3)
δ = 3.05 (1H, dd, J = 12.6, 8.7 Hz, 6-CH), 3.31–3.40 (5H, m,
-OCH3, 4-CH and 6-CH), 3.51 (1H, br s, 2-CH), 3.68 (1H, t,
J = 9.4 Hz, 3-CH), 3.76 (1H, td, J = 9.0, 2.5 Hz, 5-CH), 4.31
(1H, br s, -OH), 4.63 (1H, br s, -OH), 4.67 (1H, d, J = 3.6 Hz,
1-CH), 5.25 (1H, br s, -OH), 7.16–7.24 (3H, m, ArH), 7.48–7.51
(2H, m, ArH); 13C NMR (CDCl3) δ = 31.7(t), 57.3(q), 73.0(d),
74.2(d), 75.9(d), 76.3(d), 101.2(d), 128.7(d), 131.0(d), 132.8(s),
134.1(d); HRMS (FABϩ) Found: m/z 334.0296, Calcd for
C13H18O5Se: Mϩ = 334.0320.
Preparation of alkyl aryl chalcogenides
3ꢀ-Cholestanyl phenyl sulfide13 (2).
4-Chlorophenyl 1-tridecyl selenide (14). 95% yield; mp 44.0–
45.0 ЊC; IR (KBr) 2920, 2850, 1480, 1460, 1390, 1100, 1010,
A mixture of 3α-
1
cholestanyl bromide (4.5 mmol), PhSH (10 mmol) and KOH
(10 mmol) in hexane–EtOH (4:6 ml) was stirred for 2 days
at 60 ЊC. Then, the organic layer was extracted with CHCl3
and dried over Na2SO4. The solution was evaporated and the
residue was purified by column chromatography to give 3β-
cholestanyl phenyl sulfide in 60% yield. Mp 75.5–76.5 ЊC (lit.,13
mp 77–79 ЊC); IR (KBr) 2930, 2845, 1580, 1480, 1460, 1445,
810, 730 cmϪ1; H NMR (CDCl3) δ = 0.88 (3H, t, J = 6.9 Hz,
CH3-), 1.25 (18H, br s, -CH2-), 1.38 (2H, br t, J = 7.2 Hz, -CH2-),
1.68 (2H, quintet, J = 7.5 Hz, -CH2-), 2.88 (2H, t, J = 7.5 Hz,
-CH2-), 7.22 (2H, dt, J = 9.0, 2.3 Hz, ArH), 7.40 (2H, dt,
J = 9.0, 2.3 Hz, ArH); 13C NMR (CDCl3) δ = 14.2(q), 22.8(t),
28.4(t), 29.1(t), 29.4(t), 29.6(t), 29.6(t), 29.7(t), 29.7(t), 29.8(t),
30.1(t), 32.0(t), 128.9(s), 129.2(d), 132.9(s), 133.9(d); MS (EI)
Found: m/z 374; Anal. Calcd for C19H31ClSe: C, 61.04; H,
8.36%. Found: C, 60.82; H, 8.51%.
1435, 1380, 1090, 1020, 735, 690 cmϪ1 1H NMR (CDCl3)
;
δ = 0.59–1.97 (46H, m, cholestanyl), 3.06 (1H, tt, J = 12.2, 4.2
Hz, 3-CH), 7.19–7.30 (3H, m, ArH), 7.38–7.40 (2H, m, ArH);
MS (EI) Found: m/z 480.
4-Methoxyphenyl 1-tridecyl selenide (15). 76% yield; mp
47.0–48.0 ЊC; IR (KBr) 2920, 2850, 1600, 1495, 1290, 1250,
3ꢀ-Cholestanyl phenyl selenide14 (3). (Typical procedure) A
solution of PhSeSePh (1.5 mmol) in EtOH–THF (5:5 ml) was
treated with NaBH4, until the color of dichalcogenide dis-
appeared. Then, 3α-cholestanyl bromide (3.3 mmol) was added
to the solution and stirred overnight at 60 ЊC. The organic layer
1180, 1035, 810, 730 cmϪ1; H NMR (CDCl3) δ = 0.88 (3H, t,
1
J = 6.9 Hz, CH3-), 1.24 (18H, br s, -CH2-), 1.36 (2H, br t, J = 7.2
Hz, -CH2-), 1.64 (2H, quintet, J = 7.5 Hz, -CH2-), 2.81 (2H, t,
J = 7.5 Hz, -CH2-), 3.80 (3H, s, CH3O-), 6.81 (2H, dt, J = 9.7,
2.5 Hz, ArH), 7.46 (2H, dt, J = 9.7, 2.5 Hz, ArH); 13C NMR
J. Chem. Soc., Perkin Trans. 1, 1999, 2891–2896
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(CDCl3) δ = 14.1(q), 22.7(t), 29.1(t), 29.1(t), 29.3(t), 29.5(t),
29.6(t), 29.6(t), 29.7(t), 29.7(t), 30.2(t), 31.9(t), 55.7(q),
114.7(d), 120.3(s), 135.4(d), 159.1(s); MS (EI) Found: m/z 370;
Anal. Calcd for C20H34OSe: C, 65.02; H, 9.28%. Found: C,
64.94; H, 9.50%.
67.3(d), 68.7(d), 71.0(d), 100.2(d), 127.7(d), 129.1(d), 129.2(s),
134.2(d), 169.6(s), 170.2(s), 170.7(s); HRMS (FABϩ) Found:
m/z 474.0799, Calcd for C20H26O8Se: Mϩ = 474.0794.
12. Mp 78.5–80.0 ЊC; IR (KBr) 2980, 2930, 2880, 1745,
1735, 1580, 1380, 1245, 1225, 1155, 1100, 1040, 1020, 920, 745,
1-Adamantyl phenyl selenide4 (5). This compound was pre-
pared in 49% yield by the literature method.17 Mp 40.5–43.0 ЊC
690 cmϪ1 1H NMR (CDCl3) δ = 1.23 (3H, t, J = 7.0 Hz,
;
-OCH2CH3), 2.00 (3H, s, -OAc), 2.04 (3H, s, -OAc), 2.06 (3H, s,
-OAc), 3.13 (1H, dd, J = 11.5, 9.1 Hz, 2-CH), 3.49–3.58 (2H,
m, 5-CH and -OCH2CH3), 3.91 (1H, dq, J = 9.2, 7.1 Hz,
-OCH2CH3), 4.07 (1H, dd, J = 12.1, 2.4 Hz, 6-CH), 4.26 (1H,
dd, J = 12.1, 5.0 Hz, 6-CHЈ), 4.27 (1H, d, J = 9.1 Hz, 1-CH),
4.98 (1H, dd, J = 9.9, 9.2 Hz, 4-CH), 5.14 (1H, dd, J = 11.5, 9.2
Hz, 3-CH), 7.25–7.35 (3H, m, ArH), 7.64–7.66 (2H, m, ArH);
13C NMR (CDCl3) δ = 15.0(q), 20.7(q), 20.7(q), 20.8(q),
47.8(d), 62.3(t), 65.9(t), 69.9(d), 71.5(d), 72.8(d), 102.6(d),
126.7(s), 128.4(d), 129.1(d), 136.0(d), 169.7(s), 170.3(s),
170.8(s); HRMS (FABϩ) Found: m/z 474.0784, Calcd for
C20H26O8Se: Mϩ = 474.0794.
(lit.,4 mp 42–45 ЊC); IR (KBr) cmϪ1 1H NMR (CDCl3)
;
δ = 1.61–1.69 (6H, m, adamantyl), 1.97–1.99 (9H, br s,
adamantyl), 7.27–7.32 (2H, m, ArH), 7.34–7.38 (1H, m, ArH),
7.60–7.63 (2H, m, ArH); MS (EI) Found: m/z 292.
Phenyl 2,3,5-tri-O-benzyl-1-seleno-D-ribofuranoside (9). Com-
pound 9 was prepared in 18% yield by the literature method.18
Oil; IR (Neat) 3060, 3030, 2920, 2860, 1580, 1500, 1480, 1455,
1140, 1030, 740, 700 cmϪ1; 1H NMR (CDCl3) δ = 3.56 (1H, dd,
J = 11.0, 3.6 Hz, 5-CH), 3.63 (1H, dd, J = 11.0, 3.3 Hz, 5-CHЈ),
3.98 (1H, t, J = 5.3 Hz, 3-CH), 4.18 (1H, t, J = 5.6 Hz, 2-CH),
4.41–4.52 (3H, m, 4-CH and -OCH2Ph), 4.55 (1H, d, J = 12.2
Hz, -OCH2Ph), 4.66 (1H, d, J = 11.6 Hz, -OCH2Ph), 4.75
(1H, d, J = 12.2 Hz, -OCH2Ph), 4.80 (1H, d, J = 11.6 Hz,
-OCH2Ph), 6.08 (1H, d, J = 5.6 Hz, 1-CH), 7.23–7.35 (16H, m,
ArH), 7.40–7.42 (2H, m, ArH), 7.63–7.66 (2H, m, ArH); 13C
NMR (CDCl3) δ = 69.0(t), 72.6(t), 73.2(t), 73.4(t), 77.0(d),
78.9(d), 81.1(d), 89.2(d), 126.9(d), 127.6(d), 127.6(d), 127.8(d),
127.8(d), 127.9(d), 128.3(d), 128.3(d), 128.8(d), 131.5(s),
133.5(d), 137.6(s), 138.0(s), 138.1(s); HRMS (FABϩ) Found:
m/z (M ϩ K) 599.1050, Calcd for C32H32O4SeK: (M ϩ K)ϩ =
599.1105.
2Ј-Deoxy-2Ј-phenylseleno-3Ј,5Ј-O-(1,1,3,3-tetraisopropyl-
disiloxane-1,3-diyl)-N-(triphenylphosphoranylidene)adenosine
(13). This compound was prepared in 31% yield from the
2Ј-iodoadenosine derivative by the typical procedure at room
temperature. 2Ј-Iodoadenosine derivative was prepared from
3Ј,5Ј-O-protected adenosine by the literature method.19 Viscous
oil; IR (KBr) 3060, 2945, 2865, 1580, 1450, 1440, 1360, 1290,
1115, 1035, 885, 720, 690 cmϪ1; 1H NMR (CDCl3) δ = 0.99–1.19
(28H, m, isopropyl), 4.00–4.21 (3H, m, 4Ј-CH and 5Ј-CH),
4.74 (1H, dd, J = 7.5, 5.0 Hz, 2Ј-CH), 5.29 (1H, dd, J = 7.5,
5.8 Hz, 3Ј-CH), 6.07 (1H, d, J = 5.0 Hz, 1Ј-CH), 6.94–6.96
(3H, m, ArH), 7.30–7.33 (2H, m, ArH), 7.36 (1H, s, ArH),
7.42–7.56 (9H, m, ArH), 7.86–7.92 (7H, m, ArH); 13C NMR
(CDCl3) δ = 14.7(d), 14.9(d), 15.3(d), 15.5(d), 19.0(q), 19.1(q),
19.1(q), 19.3(q), 19.4(q), 19.4(q), 19.5(q), 51.6(d), 65.2(t),
75.3(d), 86.8(d), 92.7(d), 128.9(s), 129.3(s), 129.5(s), 129.8(d),
130.3(d), 130.4(d), 130.6(s), 130.9(d), 131.4(s), 133.9(d),
133.9(d), 135.3(d), 135.4(d), 136.9(d), 140.4(d), 151.2(s),
153.7(d), 162.9(s); HRMS (FABϩ) Found: m/z (M ϩ H)
910.2874, Calcd for C46H57N5O4PSeSi2: (M ϩ H)ϩ = 910.2858.
Phenyl
3,5-di-O-benzyl-2-deoxy-1-seleno-D-ribofuranoside
(10). Compound 10 was prepared in 5% yield by the literature
method.18 Oil; IR (Neat) 3060, 3030, 2920, 2860, 1580, 1500,
1480, 1455, 1090, 940, 740, 700 cmϪ1 1H NMR (CDCl3)
;
δ = 2.24 (1H, ddd, J = 13.7, 7.7, 6.0 Hz, 2-CH), 2.49 (1H,
J = 13.7, 6.2, 2.9 Hz, 2-CHЈ), 3.43 (1H, dd, J = 10.0, 6.2 Hz,
5-CH), 3.59 (1H, dd, J = 10.0, 5.2 Hz, 5-CHЈ), 4.09 (1H, ddd,
J = 6.0, 2.9, 2.6 Hz, 3-CH), 4.29 (1H, ddd, J = 6.2, 5.2, 2.6 Hz,
4-CH), 4.48 (1H, d, J = 11.9 Hz, -OCH2Ph), 4.52 (1H, d,
J = 11.9 Hz, -OCH2Ph), 4.54 (2H, s, -OCH2Ph), 5.84 (1H,
dd, J = 7.7, 6.2 Hz, 1-CH), 7.23–7.36 (13H, m, ArH), 7.59–
7.62 (2H, m, ArH); 13C NMR (CDCl3) δ = 41.6(t), 72.7(t),
73.3(t), 75.4(t), 82.3(d), 83.9(d), 86.6(d), 129.5(d), 129.6(d),
129.7(d), 129.7(d), 129.7(d), 130.4(d), 130.4(d), 130.9(d),
131.5(s), 136.2(d), 139.8(s), 140.1(s); HRMS (FABϩ) Found:
m/z (M ϩ K) 493.0703. Calcd for C25H26O3SeK: (M ϩ K)ϩ =
493.0686.
Radical reduction initiated by Et3B
Triethylborane in tetrahydropyran (0.15 ml, 1 M) was added
to a mixture of alkyl phenyl chalcogenide (0.30 mmol) and
organodisilane (0.45 mmol) in ethyl acetate (3.0 ml) under
aerobic conditions at room temperature, and the reaction mix-
ture was stirred for 1 h. The reaction of selenides 8, 9 and 13
was initiated by 1.2 mmol of Et3B. In the reactions of selenides
10 and 11, the starting selenides remained after 1 h, so Et3B
was added again to consume the compounds 10 and 11. After
the reaction, the solvent was evaporated and the residue was
purified by PTLC, and column chromatography, and recycling
preparative HPLC.
Ethyl 2-deoxy-2-phenylseleno-3,4,6-tri-O-acetyl-ꢁ-D-manno-
pyranoside (11) and ethyl 2-deoxy-2-phenylseleno-3,4,6-tri-O-
acetyl-ꢀ-D-glucopyranoside (12). PhSeBr (3 mmol) was added to
the solution of 3,4,6-tri-O-acetyl-D-glucal (3.1 mmol) in EtOH
(10 ml) at 0–5 ЊC, then, a small amount of K2CO3 was added.
The solution was stirred for 3 h at room temperature. After the
reaction, the residue was worked up in the usual way to give a
mixture of 2-phenylselenosugars (11:12 = 2.4:1) in 23% yield.
The stereochemistry of 11 and 12 was determined from 1H
NMR spectra of the reduction products.
Radical reduction initiated by AIBN
A solution of alkyl phenyl chalcogenide (0.30 mmol), organo-
disilane (0.75 mmol) and AIBN (0.75 mmol) in ethyl acetate
(3.0 ml) was refluxed for 14 h under an argon atmosphere. After
the reaction, the solvent was evaporated and the residue was
purified by PTLC, and column chromatography, and recycling
preparative HPLC.
11. Mp 91.0–94.0 ЊC; IR (KBr) 2975, 2910, 2880, 1740, 1580,
1
1365, 1240, 1125, 1060, 1015, 965, 745, 690 cmϪ1; H NMR
(CDCl3) δ = 1.23 (3H, t, J 7.1 Hz, -OCH2CH3), 1.68 (3H, s,
-OAc), 2.04 (3H, s, -OAc), 2.13 (3H, s, -OAc), 3.51 (1H, dq,
J = 9.8, 7.1 Hz, -OCH2CH3), 3.71 (1H, dq, J = 9.8, 7.1 Hz,
-OCH2CH3), 3.91 (1H, dd, J = 3.9, 1.3 Hz, 3-CH), 3.99 (1H,
ddd, J = 9.7, 5.0, 2.6 Hz, 5-CH), 4.15 (1H, dd, J = 12.1, 2.6
Hz, 6-CH), 4.20 (1H, dd, J = 12.1, 5.0 Hz, 6-CHЈ), 5.19 (1H, d,
J = 1.3 Hz, 2-CH), 5.41–5.48 (2H, m, 1-CH and 4-CH), 7.24–
7.28 (3H, m, ArH), 7.56–7.59 (2H, m, ArH); 13C NMR (CDCl3)
δ = 14.9(q), 20.3(q), 20.7(q), 20.7(q), 48.1(d), 62.6(t), 63.7(t),
Cholestane, adamantane, n-tridecane and methyl 6-deoxy-ꢁ-D-
glucopyranoside
These compounds were identified with the authentic samples.6
1,5-Anhydro-2,3,4,6-tetra-O-acetyl-D-galactitol20
Syrup; IR (Neat) 2980, 2870, 1750, 1435, 1370, 1240, 1050, 955,
2894
J. Chem. Soc., Perkin Trans. 1, 1999, 2891–2896

View Article Online
905 cmϪ1; 1H NMR (CDCl3) δ = 2.01 (3H, s, -OAc), 2.05 (3H, s,
-OAc), 2.06 (3H, s, -OAc), 2.15 (3H, s, -OAc), 3.29 (1H, dd,
J = 11.2, 10.3 Hz, 1-CH), 3.82 (1H, td, J = 6.5, 1.2 Hz, 5-CH),
4.09 (2H, d, J = 6.5 Hz, 6-CH), 4.19 (1H, dd, J = 11.2, 5.5 Hz,
1-CHЈ), 5.04 (1H, dd, J = 10.3, 3.4 Hz, 3-CH), 5.23 (1H, td,
J = 10.3, 5.5 Hz, 2-CH), 5.45 (1H, dd, J = 3.4, 1.2 Hz, 4-CH);
MS (FABϩ) Found: m/z (M ϩ H) 333.
152.0(d), 161.1(s); HRMS (FABϩ) Found: m/z (M ϩ H)
754.3322, Calcd for C40H53N5O4PSi2: (M ϩ H)ϩ = 754.3374.
2Ј-Deoxy-3Ј,5Ј-O-(1,1,3,3-tetraisopropyldisiloxane-1,3-diyl)-
adenosine25
Viscous oil; IR (KBr) 3330, 3170, 2945, 2865, 1650, 1600, 1465,
1
1250, 1140, 1120, 1090, 1075, 1040, 885, 700 cmϪ1; H NMR
(CDCl3) δ = 1.02–1.13 (28H, m, isopropyl), 2.64 (1H, ddd,
J = 13.3, 9.1, 7.4 Hz, 2Ј-CH), 2.71 (1H, ddd, J = 13.3, 7.5, 2.7
Hz, 2Ј-CHЈ), 3.90 (1H, ddd, J = 7.5, 4.4, 3.5 Hz, 4Ј-CH), 4.03
(1H, dd, J = 12.4, 3.5 Hz, 5Ј-CH), 4.07 (1H, dd, J = 12.4, 4.4
Hz, 5Ј-CHЈ), 4.95 (1H, dt, J = 9.1, 7.5 Hz, 3Ј-CH), 5.67 (2H, br
s, -NH2), 6.29 (1H, dd, J = 7.4, 2.7 Hz, 1Ј-CH), 8.04 (1H, s,
ArH), 8.32 (1H, s, ArH); HRMS (FABϩ) Found: m/z (M ϩ H)
494.2607, Calcd for C22H40N5O4Si2: (M ϩ H)ϩ = 494.2619.
1,4-Anhydro-2,3,5-tri-O-benzyl-D-ribitol21
Oil; IR (Neat) 3060, 3030, 2870, 1495, 1455, 1360, 1210, 1125,
1030, 740, 700 cmϪ1 1H NMR (CDCl3) δ = 3.51 (1H, dd,
;
J = 10.6, 4.3 Hz, 5-CH), 3.62 (1H, dd, J = 10.6, 3.3 Hz, 5-CHЈ),
3.91–4.09 (4H, m, 1-CH, 2-CH and 3-CH), 4.14–4.17 (1H, m,
4-CH), 4.49–4.64 (6H, m, -OCH2Ph), 7.24–7.36 (15H, m, ArH);
MS (FABϩ) Found: m/z (M ϩ K) 443.
1,4-Anhydro-2-deoxy-3,5-di-O-benzyl-D-erythropentitol22
Acknowledgements
Syrup; IR (Neat) 3060, 3030, 2860, 1495, 1455, 1365, 1205,
We are grateful for financial support from a Grant-in-Aid for
Scientific Research (10640511) from the Ministry of Education,
Science, and Culture of Japan. We thank Mr Atushi Ryokawa
for the partial preparation of organodisilanes.
1
1100, 1030, 740, 700 cmϪ1; H NMR (CDCl3) δ = 2.00–2.04
(2H, m, 2-CH), 3.48 (1H, dd, J = 10.1, 5.1 Hz, 5-CH), 3.53 (1H,
dd, J = 10.1, 5.1 Hz, 5-CHЈ), 3.90–4.10 (4H, m, 1-CH, 3-CH
and 4-CH), 4.49 (1H, d, J = 12.1 Hz, -OCH2Ph), 4.53 (1H,
d, J = 12.1 Hz, -OCH2Ph), 4.55 (2H, s, -OCH2Ph), 7.26–7.38
(10H, m, ArH); 13C NMR (CDCl3) δ = 32.7(t), 67.7(t), 71.0(t),
71.4(t), 73.6(t), 80.9(d), 83.2(d), 127.8(d), 127.8(d), 127.8(d),
128.5(d), 128.6(d), 138.3(s); MS (FABϩ) Found: m/z (M ϩ K)
337.
Notes and references
1 B. Giese, Radicals in Organic Synthesis: Formation of Carbon-
Carbon Bonds, ed. J. E. Baldwin, Pergamon Press, Oxford, 1986;
J. Fossey, D. Lefort and J. Sorba, Free Radicals in Organic
Chemistry, Wiley, Chichester, 1995.
2 C. Chatgilialoglu, K. U. Ingold and J. C. Scaiano, J. Am. Chem.
Soc., 1982, 104, 5123; J. Lusztyk, B. Maillard and K. U. Ingold,
J. Org. Chem., 1986, 51, 2457; B. Giese, B. Kopping and
C. Chatgilialoglu, Tetrahedron Lett., 1989, 30, 681; B. Giese and
K. J. Kulicke, Synlett, 1990, 91; D. H. R. Barton, D. O. Jang
and J. Cs. Jaszberenyi, Tetrahedron Lett., 1990, 31, 4681; A. Alberti
and C. Chatgilialoglu, Tetrahedron, 1990, 46, 3963; S. J. Cole,
J. N. Kirwan, B. P. Roberts and C. R. Willis, J. Chem. Soc., Perkin
Trans. 1, 1991, 103; D. H. R. Barton, D. O. Jang and J. Cs.
Jaszberenyi, Synlett, 1991, 435; D. H. R. Barton, D. O. Jang and
J. Cs. Jaszberenyi, Tetrahedron Lett., 1991, 32, 2569; D. H. R.
Barton, D. O. Jang and J. Cs. Jaszberenyi, Tetrahedron Let., 1991,
32, 7187; C. Chatgilialoglu, Acc. Chem. Res., 1992, 25, 188; C.
Chatgilialoglu, Chem. Rev., 1995, 95, 1229; M. B. Haque and
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3 M. Ballestri, C. Chatgilialoglu, K. B. Clark, D. Griller, B. Giese and
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4 D. H. R. Barton, D. O. Jang and J. Cs. Jaszberenyi, Tetrahedron,
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5 O. Yamazaki, H. Togo, G. Nogami and M. Yokoyama, Bull. Chem.
Soc. Jpn., 1997, 70, 2519.
Ethyl 2-deoxy-3,4,6-tri-O-acetyl-ꢁ-D-arabinohexopyranoside23
Oil; IR (Neat) 2980, 1745, 1440, 1370, 1240, 1130, 1050, 980
cmϪ1
;
1H NMR (CDCl3) δ = 1.22 (3H, t, J = 7.1 Hz,
-OCH2CH3), 1.82 (1H, ddd, J = 12.8, 11.5, 3.7 Hz, 2-CH), 2.01
(3H, s, -OAc), 2.04 (3H, s, -OAc), 2.10 (3H, s, -OAc), 2.23 (1H,
ddd, J = 12.8, 5.4, 1.2 Hz, 2-CHЈ), 3.46 (1H, dq, J = 9.7, 7.1 Hz,
-OCH2CH3), 3.69 (1H, dq, J = 9.7, 7.1 Hz, -OCH2CH3), 3.98
(1H, ddd, J = 10.1, 4.6, 2.3 Hz, 5-CH), 4.05 (1H, dd, J = 12.1,
2.3 Hz, 6-CH), 4.31 (1H, dd, J = 12.1, 4.6 Hz, 6-CHЈ), 4.96–
5.02 (2H, m, 1-CH and 4-CH), 5.34 (1H, ddd, J = 11.5, 9.5, 5.4
Hz, 3-CH); MS (FABϩ) Found: m/z (M Ϫ OEt) 273.
Ethyl 2-deoxy-3,4,6-tri-O-acetyl-ꢀ-D-arabinohexopyranoside24
Mp 83.5–84.5 ЊC (lit.,24 mp 80–81 ЊC); IR (KBr) 3000, 2975,
2895, 1740, 1440, 1380, 1230, 1140, 1095, 1050, 960, 920 cmϪ1
;
1H NMR (CDCl3) δ = 1.23 (3H, t, J = 7.1 Hz, -OCH2CH3), 1.75
(1H, ddd, J = 12.6, 11.5, 9.8 Hz, 2-CH), 2.03 (3H, s, -OAc), 2.04
(3H, s, -OAc), 2.09 (3H, s, -OAc), 2.31 (1H, ddd, J = 12.6, 4.8,
2.2 Hz, 2-CHЈ), 3.52–3.63 (2H, m, 5-CH and -OCH2CH3), 3.94
(1H, dq, J = 9.5, 7.1 Hz, -OCH2CH3), 4.11 (1H, dd, J = 12.2, 2.5
Hz, 6-CH), 4.30 (1H, dd, J = 12.2, 4.8 Hz, 6-CHЈ), 4.58 (1H,
dd, J = 9.8, 2.2 Hz, 1-CH), 4.96–5.06 (2H, m, 3-CH and 4-CH);
MS (FABϩ) Found: m/z (M Ϫ OEt) 273.
6 O. Yamazaki, H. Togo, S. Matsubayashi and M. Yokoyama,
Tetrahedron Lett., 1998, 39, 1921; O. Yamazaki, H. Togo,
S. Matsubayashi and M. Yokoyama, Tetrahedron, 1999, 55, 3735.
7 A mixture of 1-deoxy derivative (A) and 2-deoxy derivative (B) was
obtained as reduction products. The ratios of A and B were
determined to be 92:8 (Et3B) and 72:28 (AIBN) from 1H NMR
spectra, respectively.
8 H.-G. Korth, R. Sustmann, K. S. Gröninger, M. Leisung and
B. Giese, J. Org. Chem., 1988, 53, 4364.
2Ј-Deoxy-3Ј,5Ј-O-(1,1,3,3-tetraisopropyldisiloxane-1,3-diyl)-
N-(triphenylphosphoranylidene)adenosine
9 Direct reduction product (C) and N-deprotected reduction product
(D) was obtained. The ratios of C and D were 95:5 (Et3B) and 82:18
(AIBN), respectively.
Viscous oil; IR (KBr) 3060, 2945, 2865, 1580, 1450, 1440, 1355,
1285, 1110, 1080, 1035, 885, 720, 690 cmϪ1; 1H NMR (CDCl3)
δ = 1.01–1.11 (28H, m, isopropyl), 2.59 (1H, ddd, J = 13.2, 8.5,
7.6 Hz, 2Ј-CH), 2.67 (1H, ddd, J = 13.2, 7.5, 2.9 Hz, 2Ј-CHЈ),
3.87 (1H, d br t, J = 7.2, 4.4 Hz, 4Ј-CH), 4.02 (1H, d, J = 4.8 Hz,
5Ј-CH), 4.02 (1H, d, J = 3.9 Hz, 5Ј-CHЈ), 4.94 (1H, m, 3Ј-
CH), 6.27 (1H, dd, J = 7.6, 2.9 Hz, 1Ј-CH), 7.42–7.55 (9H,
m, ArH), 7.87–7.93 (6H, m, ArH), 7.96 (1H, s, ArH), 8.05 (1H,
s, ArH); 13C NMR (CDCl3) δ = 12.6(d), 13.0(d), 13.2(d),
13.4(d), 17.0(q), 17.0(q), 17.1(q), 17.2(q), 17.4(q), 17.4(q),
17.5(q), 17.6(q), 40.3(t), 62.5(t), 70.8(d), 82.8(d), 85.1(d),
127.1(s), 127.3(s), 128.4(d), 128.5(d), 128.6(s), 129.4(s),
131.9(d), 131.9(d), 133.4(d), 133.4(d), 137.6(d), 149.3(s),
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2896
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