Table 2 Results of metathesis of CDA by 4 and 1 or 2 at 125 uC.a,b Distribution of products (weight %)
Cycloalkanes (% by weight)
Cat.
Time/h
C10
C19
C20
C21
C29
C30
C31
C40
Sum C6–40
Insol.
% Conv. C10
1
1
1
2
2
a
48
96
144
6
58
31
7.6
83
79
b
0.4
0.6
0.8
0.1
0.1
1.7
3.7
8.5
2.0
3.2
0.4
0.6
0.9
0.1
0.1
0.1
0.2
0.5
0.0
0.0
0.4
0.9
3.0
0.3
0.3
0.1
0.2
0.6
0.0
0.0
0.1
0.4
1.1
0.1
0.1
5.7
9.2
19
4.6
5.7
18
37
53
8.7
11
42
69
92
17
21
12
See Table 1 footnotes. C10H20 (0.5 mL; 435 mg); TBE (1.3 mL; 20 mM); 1 (3.0 mg; 10 mM) or 2 (2.8 mg; 10 mM) and 4 (2.5 mg; 6.5 mM).
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nature of the catalyst. We suspect that the same factor that favors
formation of cycloheptane and other non-C8n species by catalyst 1,
i.e., a greater rate of a- to b-double-bond isomerization, also
results in a decreased rate of ring closure by the growing chain due
to the much lower reactivity of internal double-bonds; polymer-
ization is thereby favored relative to cyclooligomerization.
Cyclodecane (CDA) was also found to undergo metathesis-
oligomerization catalyzed by 4 and either 1 or 2 (Table 2). The
major cyclic products have the formula C10nH20n; the yields
decrease with increasing values of n, as is the case with COA.
Unlike with COA, no ring contraction products (carbon number
less than 10) were observed; formation of cyclononane would not
afford the same reduction in strain as is achieved in the formation
of cycloheptane from COA. However, a somewhat greater
quantity of ‘‘non-integral’’ cyclooligomers (e.g. C19H38 or
C29H58, but not cyclononane) is formed. The yields of polymer,
and oligomers with carbon number . 40, are comparable to those
obtained from COA.
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and CDA to give cycloalkanes with different carbon numbers,
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are the major product, with successively decreasing amounts of
higher cyclooligomers formed. In addition, polymerization of the
cycloalkanes can occur. Both cyclooligomerization (metathesis)
and polymerization of cycloalkanes are unprecedented. Future
work will focus on (i) controlling and understanding selectivity
with respect to both the polymer : cycloalkane ratios as well as the
Mw’s of either type of product, and (ii) extending these reactions to
functionalized saturated molecules in an effort to make the
corresponding functionalized macrocycles or polymers.
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We thank the NSF for support of this work under the auspices
of the Center for Enabling New Technologies through Catalysis
(CENTC), and Prof. Geoffrey W. Coates for GPC analysis and
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Notes and references
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Chem. Commun., 2008, 253–255 | 255