C O M M U N I C A T I O N S
Scheme 1. Carbon-Carbon Coupling Reaction Catalyzed by the
Table 1. Dimerization of Alkenes Catalyzed by the Nitrosonium
NO+ Cation
Cationa
conversion, mol %
dimer yield, mol %e
alkene
A
B
A
B
cyclohexeneb
57
91
96
82
84
89
95
74
77
42
65
90
93
84
81
na
88
79
74
47
77
83
72
79
46
79
54
27
41
50
95
92
71
80
53
na
56
32
45
61
1-methylcyclohexeneb
limoneneb
Chart 1. Alkylation of Arenes with Alkenes Catalyzed by NO+a
1,1-diphenylethenec
2,3-dimethyl-2-buteneb
2-methyl-2-hepteneb
2-methyl-1-hepteneb
trans-2-octeneb
1-octeneb
cyclooctened
a Reaction conditions: (A) 2 mmol alkene, 0.1 mmol NOBF4, 0.01
mmol Na(BArf)4, 30 °C, h. (B) mmol alkene, 0.01 mmol
3
2
NO+-POM, 70 °C, 3 h. Reactions were quantified by GC and identified
by GC-MS or reference standards where available. b For these
compounds a large number (4 to ∼14 depending on the substrate) of
isomeric dimers were observed by GC-MS. c The major product
(>95%) was 1,1,4,4-tetraphenyl-2-butene; the remaining product was
1-methyl-1,3,3-triphenylindane. d For systems A and B, 57 and 37%,
respectively, of the total products was 3-methylcycloheptene. e The
remaining products were oligomers of the alkene.
amounts of C-C coupling products were obtained. The reaction
of alkenes with aromatic substrates represents an interesting
alternative to Friedel-Crafts type alkylations with alkenes under
mild reaction conditions.
Acknowledgment. The research was supported by the German
Federal Ministry of Education and Research through the German-
Israeli Project Cooperation (DIP-G7.1), the Israel Science Founda-
tion, and the Kimmel Center for Molecular Design. R.N. is the
Rebecca and Israel Sieff Professor of Organic Chemistry. Anat Milo
is thanked for the BET measurements.
a Reaction conditions: (A) 1 mmol alkene, 9 mmol arene, 0.1 mmol
NOBF4, 0.01 mmol Na(BArf)4, 30 °C, 3 h; (B) 1 mmol alkene, 9 mmol
arene, 0.01 mmol NO+-POM, 70 °C, 3 h. The results for conditions B are
in parentheses. Reactions were quantified by GC and identified by GC-MS
or reference standards where available: (a) selectivity is given as mol % of
the noted products; (b) the major products were alkene dimers.
Supporting Information Available: Full experimental details, a
Hammett graph for arene alkylation, BET measurements. This material
(vii) Using the alkylation of benzene with cyclohexene as a benchmark,
the possibility of NO+-POM catalyst recycle/recovery was studied.
Although trace amounts of catalytic species appear to be lost via
formation of nitrogen containing products, the NO+-POM catalyst
showed only a minimal loss of reactivity (5%) from cycle to cycle.
(viii) Notably NO+-POM acted much differently than the known
phosphotungstic acid, H3PW12O40. Thus, in the alkylation of benzene
with cyclohexene no alkylation was observed, while attempts at alkene
dimerization (e.g., 1-octene) led only to double-bond isomerization
(10%). Upon use of high surface area 5 wt % H3PW12O40 supported
on silica (∼500 m2/g)10 there also was no reactivity observed for the
1-octene dimerization reaction, while the benzene alkylation showed
only a 16% conversion versus 82% for NO+-POM (Chart 1). The
results appear to indicate that for the NO+-POM catalyst the POM
functions only as an inert carrier for NO+; the low nucleophilicity of
such polyanions may also increase the electrophilicity of the nitroso-
nium cation catalyst.
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The activation of alkenes by NO+ toward alkene-alkene dimer-
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