Carbanion Generation
FULL PAPER
Table 5. Competition experiments of arylheteroatom compounds.
treated with nBuLi (71.4 mL, 1.54m solution in hexane, 0.11 mmol) at
À788C. After stirring for 0.5 h at this temperature, benzaldehyde
(10.6 mL, 0.11 mmol) was added. The resulting mixture was slowly
warmed to room temperature over 0.5 h. The reaction mixture was
quenched with saturated aqueous NH4Cl solution (0.5 mL) and was ex-
tracted with ethyl acetate (0.5 mLꢁ 3). The organic layer was washed
with saturated aqueous NaCl solution, dried over MgSO4, filtered, and
concentrated under reduced pressure to give a crude mixture. The yield
1
(97%) of 2A was determined by H NMR spectroscopy using pyrazine as
Entry
X
Yield[a] [%]
6A/22
Reactivity
ACHTUNGTRENNUNG
[X/I][b]
an internal standard. Purification by silica gel chromatography afforded
2A in 92% yield (20.4 mg) as a colorless solid. Rf =0.32 (ethyl acetate/
hexane 25:75); m.p. 39.8–41.68C; 1H NMR (400 MHz, CDCl3): d=7.36–
À
6A
22
23
1
2
3
4
Bi
Sb
Te
I
G
0.1
0.8
1.9
4.6
7.5
12.5
8.0
23.0
42.0
50.5
54.5
0.013
0.064
0.24
0.025
0.12
0.47
–
7.25 (m, 5H; Ar H), 4.91 (s, 1H; CH), 4.18 (q, 3J
N
G
3
ACHTUNGTRENNUNG
CH2), 3.57 (s, 1H; OH), 1.27 (t, J
N
CH3), 1.10 ppm (s, 3H; CH3); 13C NMR (100 MHz, CDCl3): d=178.1,
140.1, 127.9, 127.8, 78.9, 61.1, 47.7, 23.3, 19.1, 14.3 ppm; IR (KBr): n˜ =
710, 1049, 1153, 1267, 1705, 2980, 3499 cmÀ1; HRMS (EI): m/z: calcd for
C13H18O3: 222.1256 [M+]; found: 222.1254.
9.0
0.52
[a] Determined by gas chromatography using tetradecane as an internal
standard. [b] Reactivity of heteroatom group after compensation of the
effect of the aryl group.
General procedure for synthesis of w-deuterated PMMA 9F (Table 3
entry 1):
A
solution of 8a (Mn =3000, Mw/Mn =1.21, 186.3 mg,
Our reactivity index between organotellurium and orga-
noiodide is opposite to the one reported by Sonoda and co-
workers.[75] We believe that the results must be due to the
substituent on the tellurium atom. Sonoda and co-workers
used butyl phenyl telluride, and we used 3g and 6h. In the
case of 3g, the formation of stable enolate species decreases
the activation energy for the formation of the ate complex.
In the case of 6h, the presence of two aryl groups in the
molecule stabilizes the ate complex and thus decreases the
activation energy for the formation of the ate complex. The
results suggest that the substituent on the heteroatom also
influences the reactivity of the exchange reaction.
0.062 mmol) in THF (1.2 mL) was treated with nBuLi (45.0 mL , 1.51m
solution in hexane, 0.068 mmol) at À788C. After stirring for 0.5 h at this
temperature, DCl (18.5 mL, 6.49m in D2O, 0.12 mmol) was added. The re-
sulting mixture was stirred for 1 h at this temperature, and was slowly
warmed to room temperature over 2 h. The reaction mixture was
quenched with saturated aqueous NaHCO3 solution (0.5 mL), and ex-
tracted with CHCl3 (0.5 mLꢁ3). The organic layer was washed with satu-
rated aqueous NaCl solution, dried over MgSO4, filtered, and concentrat-
ed under reduced pressure. The residue was dissolved in CHCl3 (1 mL)
and poured into vigorously stirred hexane (50 mL). The precipitated
polymer was collected by suction and was dried under vacuum at 408C to
give PMMA in 99% (185.8 mg) with Mn =3000 and Mw/Mn =1.21. Incor-
poration of w-deuterium was confirmed by 2H NMR spectroscopy (Fig-
ure S3 in the Supporting Information). MALDI-TOF MS analysis also in-
dicated the formation of the desired w-end-deuterated PMMA with Mn =
2700 and Mw/Mn =1.04 (Figure 1).
General procedure for competition experiments between 3 and 2 f: A so-
lution of 3b (22.4 mL, 0.2 mmol), 2 f (22.4 mL, 0.2 mmol), and benzalde-
hyde (61.0 mL, 0.60 mmol) in THF (1.0 mL) was cooled to À788C, and
nBuLi (26.3 mL, 0.04 mmol) was added to this mixture. After 15 min stir-
ring at this temperature, the reaction was quenched by the addition of
AcOH/MeOH. After extractive workup, the yields of alcohols 3A, 2A,
and 21 were determined by GC analysis with tetradecane as an internal
standard. The same reaction was repeated six times (Table S3 in the Sup-
porting Information), and the yields of four experiments excluding the
highest and lowest yields were averaged (Table 4).
Conclusion
Generation of carbanions from organostibine and organobis-
muthine compounds through stibine–metal and bismuthine–
metal exchange reactions was investigated. The exchange re-
actions proceeded quantitatively to generate the corre-
sponding carbanions with several organometallic reagents.
The exchange reactions occurred with high chemoselectivity,
and a variety of polar functional groups could be tolerated.
The resulting highly functionalized carbanions were utilized
for carbon–carbon bond formation with various electro-
philes. The advantage of this method was exemplified in the
selective functionalization of polymer ends, prepared by or-
ganostibine- and organobismuthine-mediated living radical
polymerization to give a variety of structurally well-defined
w-functionalized polymers. In addition to the synthetic utili-
ty, this work provides insight into the relative reactivities of
heavier organoheteroatom compounds in heteroatom–metal
exchange reactions. We believe that this work opens new
possibilities for synthetic application of organostibines and
organobismuthines in carbanion chemistry.
Acknowledgements
This work was partly supported by the Nagase Science Foundation, a
Grant-in-Aid for Scientific Research from the Ministry of Education,
Culture, Sports, Science and Technology, Japan, and the Core Research
for Evolution Science and Technology (CREST), Japan, Science and
Technology Agency. E.K. acknowledges the receipt of a Japan Society for
the Promotion of Science (JSPS) Fellowship for Young Scientists.
[1] E. Negishi, Organometallics in Organic Synthesis, Vol. 1, Wiley, New
York, 1980, pp. 91–285.
[2] Main Group Metals in Organic Synthesis (Eds.: H. Yamamoto, K.
Oshima), Wiley-VCH, Weinheim, 2005.
Experimental Section
General procedure of the exchange reaction with nBuLi (Table 1,
entry 1): A solution of 2a (20.6 mL, 0.10 mmol) in THF (0.5 mL) was
Chem. Eur. J. 2011, 17, 5272 – 5280
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
5279
Kayahara, Eiichi
