Journal of the American Chemical Society
COMMUNICATION
consumed in 45 min under 20 atm of ethylene when 1 mol %
Mo(NAr)(CHCMe2Ph)(Pyr)(OHIPT)3 (Pyr = NC4H4À) was
employed. The reason for such a low level of activity might be
that the unsubstituted molybdacyclobutane does not readily
lose ethylene. Detailed NMR studies have shown that a
Mo(CH2CH2CH2) species is converted to a Mo(CH2)(CH2CH2)
intermediate with kf = 14 500 sÀ1 and kr = 4900 sÀ1 in the case of the
metallacyclobutane Mo(NAr)(C3H6)(OBr2Bitet)(Me2Pyr), where
OBr2Bitet is the biphenolate in 1a and Me2Pyr = NC4Me2H2À.7 In
contrast, for the same transformation in Mo(NAr)(C3H6)(OHIPT)-
(Pyr), kf and kr were found to be 1.8 and 9.0 sÀ1, respectively (20 °C,
toluene-d8 in both cases). Differences in the kf values (by a factor of
∼8000) and the equilibrium constants (3.0 and 0.2, respectively)
could account for the inability of the OHIPT-bearing catalysts tried to
date to promote Z-selective ethenolysis efficiently.
’ ACKNOWLEDGMENT
This research was funded by the National Science Foundation
(CHE-0841187 to R.R.S.) and the National Institutes of Health
(GM-59426 to R.R.S. and A.H.H.). We thank Materia, Inc., for a
gift of 5-decenylacetate.
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required to be approximately perpendicular to the MdCH2 axis
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be lost readily.10
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ethylene,1 and that 1a is not an especially successful Z-selective
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interconversion and relative rates of reaction of diastereomers
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Molybdenum-catalyzed Z-selective ethenolysis should allow
access to a large variety of E olefins that otherwise would be more
difficult to prepare in high stereoisomeric purity through alter-
native methods. This indirect synthesis of E olefins complements
the direct synthesis of Z olefins through Z-selective metathesis
reported in earlier papers. The design and development of
more efficient catalyst systems and exploration of the scope of
Z-selective ethenolysis are in progress.
’ ASSOCIATED CONTENT
S
Supporting Information. Experimental procedures and
b
spectral and analytical data for all reaction products. This material
’ AUTHOR INFORMATION
Corresponding Author
11514
dx.doi.org/10.1021/ja205002v |J. Am. Chem. Soc. 2011, 133, 11512–11514