Selective ring-opening cross-metathesis of cycloolefins

Details Selective ring-opening cross-metathesis of cycloolefins Selective ring-opening cross-metathesis of cycloolefins

2002-04-01

2004-10-12

Harlan, Robert D. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S145000, C526S170000, C526S172000, C526S190000, C526S192000, C526S193000, C526S204000, C526S308000, C526S340300, C526S348200, C548S103000, C502S155000, C502S167000

Reexamination Certificate

active

06803429

ABSTRACT:

TECHNICAL FIELD
This invention relates generally to a method for carrying out an olefin metathesis reaction using a Group 8 transition metal complex as a catalyst. More particularly, the invention relates to a method for carrying out a ring-opening cross-metathesis (“ROCM”) reaction using the aforementioned catalyst, in which a cycloolefin and a second olefinic reactant are selected with respect to their relative reactivity in the ROCM reaction. Methods are also provided for the catalysis of regioselective ROCM reactions and ROCM reactions involving at least one functionalized olefinic reactant.
BACKGROUND OF THE INVENTION
The flexibility of the olefin metathesis reaction allows the efficient production of highly functionalized, unsaturated polymers and small molecules. Grubbs et al. (1998)
Tetrahedron
54, 4413-4450; Randall et al. (1998)
J. Mol. Cat. A
-
Chem.
133, 29-40; Trnka and Grubbs (2001)
Acc. Chem. Res.
34, 18-29. Many synthetically relevant applications that involve more than one type of metathetical transformation utilize ruthenium catalysts such as (I) and molybdenum catalysts such as (II)
wherein “Cy” is a cycloalkyl group such as cyclohexyl or cyclopentyl. See Schwab et al. (1995)
Angew. Chem., Int. Ed. Engl.
34, 2039-2041; Schwab et al. (1996)
J. Am. Chem. Soc.
118, 100-110. Notably, the combination of ring-opening metathesis polymerization (ROMP) and cross-metathesis (CM) produces unique telechelic and multiple-block copolymers with novel properties. Chung et al. (1992)
Macromolecules
25, 5137-5144; Hillmyer et al. (1997)
Macromolecules
30, 718-721; Maughon et al. (2000)
Macromolecules
33, 1929-1935; Morita et al. (2000)
Macromolecules
33, 6621-6623; Bielawski et al. (2000)
Angew. Chem. Int. Ed. Engl.
39:2903-2906. For a review on telechelic polymers, see E. J. Goethals, Telechelic Polymers: Synthesis and Applications, CRC, Boca Raton, Fla., 1989. The synthesis of substituted polyethers has also been achieved by the ring closing metathesis (RCM) of a short linear molecule followed by ROMP of this new monomer. Marsella et al. (1997)
Angew. Chem. Int. Ed. Engl.
36, 1101-1103; Maynard et al. (1999)
Macromolecules
32, 6917-6924. With regard to small molecules, ring opening-ring closing “tandem” sequences allow the rapid construction of mutiply fused ring systems, which include those in complex natural products. In each of these cases the product of one metathesis event is directly available for the next, which allows multiple metathesis routes to be synthetically exploited.
A variation on this theme that remains largely unexplored is ring-opening cross-metathesis (“ROCM”), illustrated in the following scheme:
ROCM actually involves a tandem sequence in which a cycloolefin is opened and a second, acyclic olefin is then crossed onto the newly formed termini. The wide synthetic availability of cycloolefins makes this route attractive, and cyclic compounds are particularly important in synthesis. Most significantly, ring systems are key to stereochemical control; the understanding of ring conformation often presents the most expeditious route for stereocenter installation. The ability to take these general carbocycles to highly functionalized linear molecules (which, ideally, would have differentially protected termini) would therefore be extremely valuable to the synthetic chemist.
Previous work in this area has focused on highly strained cyclobutene and norbornene derivatives, as illustrated in the following schemes:
Randall et al. (1995)
J. Am. Chem. Soc.
117:9610-9611; Snapper et al. (1997)
J. Am. Chem. Soc.
119:1478-1479; Limanto et al. (2000)
J. Am. Chem. Soc.
122:8071-8072; Schrader et al. (2000)
Tetrahedron Lett.
41:9685-9689.
Both systems typically utilize steric congestion to disfavor ROMP relative to ROCM, which imposes stringent restrictions on the scaffolds open to this synthetic method. A more practical route would involve systems in which cross-metathesis can compete with polymerization, thereby directly limiting the size of the molecules produced. The invention is addressed, in part, to such a catalytic reaction, wherein the reactants as well as the catalyst are selected to maximize production of a monomeric or oligomeric product relative to the production of a telechelic polymer, via an ROCM route. The invention is also addressed to a method for producing monomers and oligomers that are “end differentiated” rather than symmetrical, enhancing the selectivity and versatility of the ROCM reaction products in further synthetic processes.
Recently, significant interest has focused on the use of N-heterocyclic carbene ligands as superior alternatives to phosphines. See, e.g., Trnka and Grubbs, supra; Bourissou et al. (2000)
Chem. Rev.
100:39-91; Scholl et al. (1999)
Tet. Lett.
40:2247-2250; Scholl et al. (1999)
Organic Lett.
1(6):953-956; and Huang et al. (1999)
J. Am. Chem. Soc.
121:2674-2678. N-heterocyclic carbene ligands offer many advantages, including readily tunable steric bulk, vastly increased electron donor character, and compatibility with a variety of metal species. In addition, replacement of one of the phosphine ligands in these complexes significantly improves thermal stability. The vast majority of research on these carbene ligands has focused on their generation and isolation, a feat finally accomplished by Arduengo and coworkers within the last ten years (see, e.g., Arduengo et al. (1999)
Acc. Chem. Res.
32:913-921). Representative of these second generation catalysts are the four ruthenium complexes (IVA), (IVB), (VA) and (VB):
In the above structures, Cy is as defined previously, “IMes” represents 1,3-dimesityl-imidazol-2-ylidene
and “IMesH
2
” represents 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene
These transition metal carbene complexes, particularly those containing a ligand having the 4,5-dihydroimidazol-2-ylidene structure such as in IMesH
2
, have been found to address a number of previously unsolved problems in olefin metathesis reactions, and are the preferred catalysts for use in conjunction with the novel ROCM methodology.
SUMMARY OF THE INVENTION
The present invention is addressed to the aforementioned need in the art, and provides a novel process for carrying out selective ring opening cross metathesis of a cycloolefin, which may or may not be a strained cyclic structure. More specifically, the method involves a catalyzed ring-opening cross-metathesis (ROCM) reaction between a cyclic olefin and a second olefinic reactant, wherein the cyclic olefin is contacted with the second olefinic reactant in the presence of a Group 8 transition metal alkylidene catalyst under conditions and for a time period effective to allow the ROCM reaction to occur. The catalyst has the structure of formula (V)
in which:
M is a Group 8 transition metal, particularly Ru or Os;
X
1
and X
2
may be the same or different, and are anionic ligands or polymers;
R
1
is selected from the group consisting of hydrogen, hydrocarbyl, substituted hydrocarbyl, heteroatom-containing hydrocarbyl, substituted heteroatom-containing hydrocarbyl, and carboxyl;
R
2
is selected from the group consisting of hydrogen, hydrocarbyl, substituted hydrocarbyl, heteroatom-containing hydrocarbyl, and substituted heteroatom-containing hydrocarbyl;
L is a neutral electron donor ligand; and
L
1
is a neutral electron donor ligand having the structure of formula (VI)
In structure (VI):
X and Y are heteroatoms selected from N, O, S, and P;
p is zero when X is O or S, and is 1 when X is N or P;
q is zero when Y is O or S, and is 1 when Y is N or P;
Q
1
, Q
2
, Q
3
, and Q
4
are linkers, e.g., hydrocarbylene (including substituted hydrocarbylene, heteroatom-containing hydrocarbylene, and substituted heteroatom-containing hydrocarbylene, such as substituted and/or heteroatom-containing alkylene) or —(CO)—;
w, x, y and z are independently zero or 1; and
R
3
, R
3A
, R
4
, and R
4A
are independently selected from the group consisting of hydrogen, hydrocarbyl, substituted hydrocarbyl, heteroatom-containing hydrocarbyl, and substituted he

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