2
Y. UCHIYAMA ET AL.
Scheme 1. Wittig reactions of non-stabilized phosphonium ylides 1 bearing a phosphaheteratriptycene skeleton (M ¼ P, As, Sb, PhSi, PhGe, PhSn, n-BuSn)
with PhCHO.
Table 1. Yields and (E)/(Z) ratios of olefins produced in the Wittig reaction.
[6]
ꢀ
a
Entry
M
Electronegativity
Isomerization temperature ( C)
Yield (%)
(E)/(Z) ratio
1
2
3
4
5
6
7
8
a
P
2.19
2.18
2.05
2.02
1.90
2.01
1.96
1.96
0
15
32
87
43
39
72
34
45
49/51
65/35
87/13
74/26
38/62
83/17
79/21
74/26
As
–20
–40
–60
–20
–50
–50
–60
[3,4]
Sb
Bi
PhSi
PhGe
PhSn
n-BuSn
31
1
Observed by VT- P{ H} NMR spectroscopy.
[6]
tendency of electronegativity , affecting M–C polarization of and Technology of Japan and Kitasato University Research Grant for
Young Researchers.
a phosphaheteratriptycene skeleton. On the other hand,
Group 14 elements substituted by the phenyl group at
another bridgehead position did not show the similar electric
References
[6]
effect based on the electronegativity , judging from the iso-
ꢀ
ꢀ
[1] Maryanoff, B. E.; Reitz, A. B. The Wittig Olefination Reaction
and Modifications Involving Phosphoryl-Stabilized Carbanions.
Stereochemistry, Mechanism, and Selected Synthetic Aspects.
Chem. Rev. 1989, 89, 863–927.
merization, which was observed at –20 C for PhSi, –50 C
ꢀ
for PhGe, and –50 C for PhSn (Table 1, entries 5–7). For the
Wittig reaction bearing a phosphastannatriptycene skeleton,
ꢀ
the substituent effect of phenyl and n-butyl groups (–50 C
[
2] Maryanoff, B. E.; Reitz, A. B.; Mutter, M. S.; Inners, R. R.;
Almond, Jr., H. R.; Whittle, R. R.; Olofson, R. A.
Stereochemistry and Mechanism of the Wittig Reaction.
Diasteromeric Reaction Intermediates and Analysis of the
Reaction Course. J. Am. Chem. Soc. 1986, 108, 7664–7678.
ꢀ
for PhSn and –60 C for n-BuSn (Table 1, entries 7,8)) on the
isomerization temperature was observed and an equilibrium
between cis-1,2-oxaphosphetane and an unidentified species
3
1
1
was detected by VT- P{ H} NMR spectroscopy. The investi-
gation is in progress.
[3] Uchiyama, Y.; Ohtsuki, T.; Murakami, R.; Shibata, M.;
Sugimoto, J. (E)-Selective Wittig Reactions between
Nonstabilized Phosphonium Ylide Bearing
a
a
Phosphastibatriptycene Skeleton and Benzaldehydes. Eur. J. Org.
Chem. 2017, 1, 159–174.
Acknowledgment
The authors thank Emeritus Prof. Takayuki Kawashima for useful advices.
[4] Uchiyama, Y.; Ohtsuki, T.; Murakami, R.; Shibata, M.;
Sugimoto, J. E-Selective Wittig Reactions Using a Nonstabilized
Phosphonium Ylide Bearing a Phosphastibatriptycene Skeleton
with Benzaldehydes under Salt-Free Conditions. Phosphorus,
Sulfur Silicon Relat. Elem. 2016, 191, 1523–1526.
Disclosure statement
No potential conflict of interest was reported by the authors.
[
5] Uchiyama, Y.; Ohtsuki, T.; Murakami, R.; Sugimoto, J.
Wittig Reactions of Phosphonium Ylides Bearing the
Phosphastibatriptycene Skeleton with Carbonyl Compounds.
Phosphorus, Sulfur Silicon Relat. Elem. 2015, 190, 633–637.
Funding
This study was partially supported by
Encouragement of Young Scientists (B) to Y. U. (No.16750041 and
No.18750037) from the Ministry of Education, Culture, Sports, Science,
a
Grant-in-Aid for
[6] Emsley, J. The Elements, 3rd ed.; Oxford University Press: New
York, 1998; pp 22–23, 26–27, 36–37, 86–87, 152–153, 190–191,
214–215.