A. J. Clark et al. / Tetrahedron Letters 42 (2001) 2003–2005
2005
OMe group 2c was more efficient than 2b. Groups at
the 5-position can inductively alter the electron density
of the pyridine nitrogen and mesomerically that of the
imine nitrogen. For each substituent a balance of both
these effects will determine the overall rate of the
reaction. If the inductive effect on the pyridine nitrogen
is the dominant feature then the order of activity/rate
of reaction would be expected to follow 2e>2a>2f>2d
Vanzanden, M. N. A.; Hiemstra, H.; Speckamp, W. N. J.
Org. Chem. 1994, 59, 1993. For ATRP: (f) Wang, J.-S.;
Matyjaszewski, K. J. Am. Chem. Soc. 1995, 117, 5614; (g)
Grimaud, T.; Matyjaszewski, K. Macromolecules 1997,
30, 2216; (h) Matyjaszewski, K.; Patten, T. E.; Xia, J. J.
Am. Chem. Soc. 1997, 119, 574.
4. For ATRC: Clark, A. J.; Duncalf, D. J.; Filik, R. P.;
Haddleton, D. M.; Thomas, G. H.; Wongtap, H. Tetra-
hedron Lett. 1999, 40, 3807; (b) Clark, A. J.; Filik, R. P.;
Thomas, G. H. Tetrahedron Lett. 1999, 40, 4885; (c)
Clark, A. J.; Dell, C. P.; Ellard, J. M.; Hunt, N. A.;
McDonagh, J. P. Tetrahedron Lett. 1999, 40, 8619. For
ATRP: (d) Haddleton, D. M.; Clark, A. J.; Crossman,
M. C.; Duncalf, D. J.; Morsley, S. R.; Heming, A. M.;
Shooter, A. J. J. Chem. Soc., Chem. Commun. 1997, 1734;
(
paralleling s ). On the other hand, if the electronic
m
mesomeric effect of substituents onto the imine nitro-
gen was dominant then the order would be expected to
be 2f>2e>2a>2d (paralleling s ). Our results show that
p
in the ATRC of 3 the rate of reaction was found to
follow the order 2e>2a>2f>2d, suggesting that inductive
effects onto the pyridine nitrogen are the dominant
features for this class of ligands in cyclisation reactions.
Thus, the rates of ATRC and ATRP reactions may well
parallel the basicity of the ligands themselves. This fits
(
e) Haddleton, D. M.; Duncalf, D. J.; Clark, A. J.;
Crossman, M. C.; Kukulj, D. New J. Chem. 1998, 22,
15; (f) Haddleton, D. M.; Duncalf, D. J.; Kukulj, D.;
3
3
in with the observation that more basic sp hybridised
Heming, A. M.; Shooter, A. J.; Clark, A. J. J. Mater.
Chem. 1998, 8, 1525; (g) Haddleton, D. M.; Crossman,
M. C.; Dana, B. H.; Duncalf, D. J.; Heming, A. M.;
Kukulj, D.; Shooter, A. J. Macromolecules 1999, 32,
amine ligands (TMEDA, N,N,N%,N%,N¦-pentamethyldi-
ethylenetriamine and tris(N,N-dimethylaminoethylene)-
10
amine) are more active catalysts for both ATRC of 3
5
d–e
and ATRP of MMA.
Reaction with the most induc-
2110.
tively electron withdrawing group, ligand 2d, caused a
significant decrease in the rate of both the ATRC
reaction of 3 and the ATRP reaction of MMA.
Although this may be due to the electronic effects
mentioned above, the possibility of the NO2 group
competitively complexing the metal and changing the
nature of the catalyst cannot be ruled out at this time.
The observation that with ligand 2d polymerisation of
MMA proceeded with all the characteristics of a ‘nor-
mal’ free radical polymerisation confirms that initiation
is relatively slow compared to propagation.
5
. For ATRC, see: (a) Forti, L.; Ghelfi, F.; Pagnoni, U. M.
Tetrahedron Lett. 1996, 37, 2077; (b) Forti, L.; Ghelfi, F.;
Libertini, E.; Pagnoni, U. M. E.; Soragni, E. Tetrahedron
1997, 53, 17761; (c) Ghelfi, F.; Bellesia, F.; Forti, L.;
Ghirardini, G.; Grandi, R.; Libertini, E.; Montemaggi,
M. C.; Pagnoni, U. M.; Pinetti, A.; DeBuyck, D.; Par-
sons, A. F. Tetrahedron 1999, 55, 1687. For ATRP, see:
(
7
d) Xia, J.; Matyjaszewski, K. Macromolecules 1997, 30,
697; (e) Xia, J.; Gaynor, S. G.; Matyjaszewski, K.
Macromolecules 1998, 31, 5958.
6
. Haddleton, D. M.; Clark, A. J.; Duncalf, D. J.; Heming,
A. M.; Kukulj, D.; Shooter, A. J. J. Chem. Soc., Dalton
Trans. 1998, 1799.
References
7
8
9
. Details of the preparation of the ligands 2a–2f will be
published separately.
1
. Iqbal, J.; Bhatia, B.; Nayyar, N. K. Chem. Rev. 1994, 94,
19.
. Due to the poor yield in the synthesis of 2f it was not
examined as a catalyst in the polymerisation reactions.
. 2a (70 min, 1.18; 130 min, 1.16; 170 min, 1.17; 240 min,
1.18): 2d (70 min, 1.16; 130 min, 1.17; 170 min, 1.19; 240
min, 1.15): 2e (70 min, 1.23; 130 min, 1.25; 170 min, 1.24;
240 min, 1.31; 1260 min, 1.47).
5
2. (a) Matyjaszewski, K. Chem. Eur. J. 1999, 5, 3095; (b)
Patten, T. E.; Matyjaszewski, K. Acc. Chem. Res. 1999,
3
2, 895.
3. For ATRC: (a) Nagashima, H.; Ozaki, N.; Ishii, M.;
Seki, K.; Washiyama, M.; Itoh, K. J. Org. Chem. 1993,
5
8, 464; (b) Iwamatsu, S.-I.; Matsubara, K.; Nagashima,
10. Clark, A. J.; De Campo, F.; Deeth, R. J.; Filik, R. P.;
Gatard, S.; Hunt, N. A.; Last e´ cou e` res, D.; Thomas, G.
H.; Verlhac, J.-B.; Wongtap, H. J. Chem. Soc., Perkin
Trans. 1 2000, 671.
H. J. Org. Chem. 1999, 64, 9625; (c) Iwamatsu, S.-I.;
Kondo, H.; Matsubara, K.; Nagashima, N. Tetrahedron
1
999, 55, 1687; (d) Udding, J. H.; Tuijp, K. C. J. M.;
.
.