2-Methyltetrahydrofuran as a Solvent of Choice for Spontaneous Metathesis/Isomerization Sequence

Abstract

A new protocol for ring-closing metathesis/isomerization sequence was developed. The reactions of selected dienes were performed in overheated 2-methyltetrahydrofuran at 120 °C and provided a wide range of cyclic vinyl ethers and amides with good yields and selectivities. Computational analysis suggests that the relative yield of products depends on a thermodynamically driven process on the basis of relative stabilities of isomers.

Towards Sustainable Catalysis – Highly Efficient Olefin Metathesis in Protic Media Using Phase Labelled Cyclic Alkyl Amino Carbene (CAAC) Ruthenium Catalysts

“…[2,3] The most frequently used olefin metathesis catalysts utilize Re, W, Mo and Ru compounds with the latter being the most preferable metal in homogeneous systems [4] showing exceptional activity in chlorinated solvents and toluene (Scheme 1). [5][6][7][8][9] Ample effort has already been made to extend the Ru-based catalyst for applications in environmentally benign, protic [10,11] or aprotic solvents [12,13] by introducing appropriate phase tags to the parent complexes. [14] Yet, the presently known arsenal of such Ru olefin metathesis catalysts, including numerous quaternary amino derivatives, [10][11][14][15][16][17][18][19][20] is far from industrial practicability as too high, 2-5 mol % catalyst loadings are required to achieve reasonable substrate conversions.…”

4-Methyltetrahydropyran as a Convenient Alternative Solvent for Olefin Metathesis Reaction: Model Studies and Medicinal Chemistry Applications

“…On the other hand, a valuable green solvent, 2-MeTHF, was found to promote C–C double bond isomerization during the olefin metathesis course. 38 Also, the solvent price and capital outlay related to its purification, handling, and disposal, the aspects of seasonal availability, and last but not least the environmental issues (sometimes hard to be a priori predicted) 39 shall be considered in each case.…”

“…They are also easily degraded by oxidative pathways, , and a number of ether solvents, such as Et 2 O, i -Pr 2 O, and THF, are known to undergo auto-oxidation and can develop substantial amounts of peroxides during storage. On the other hand, a valuable green solvent, 2-MeTHF, was found to promote C–C double bond isomerization during the olefin metathesis course . Also, the solvent price and capital outlay related to its purification, handling, and disposal, the aspects of seasonal availability, and last but not least the environmental issues (sometimes hard to be a priori predicted) shall be considered in each case.…”

Ethyl Lactate: A Green Solvent for Olefin Metathesis

“…Again, the expected product 2 e was isolated in very good isolated yield using [Ru]‐3 as catalyst, whereas [Ru]‐2 gave slightly lower yield (72 %, entry 10). Also, the RCM reaction of naphthalene derivative 1 f resulted in the isolation of the desired 7‐membered cyclic ether with good yield and excellent selectivity (similar substrates tend to undergo unwanted C−C double bond isomerization) . Interestingly, although catalyst [Ru]‐3 shows good overall efficiency, the RCM reaction of more challenging trisubstituted diene 1 g was accomplished in 64 % isolated yield only.…”

“…Also, the RCM reaction of naphthalene derivative 1f resultedi nt he isolation of the desired 7-membered cyclic ether with good yield and excellent selectivity (similar substrates tend to undergo unwanted CÀCd ouble bond isomerization). [40] Interestingly,a lthough catalyst [Ru]-3 shows good overall efficiency,t he RCMr eactiono fm ore challenging trisubstitutedd iene 1g was accomplished in 64 %i solated yield only. Furthermore, we werep leased to see that the enyne cycloisomerization of 1h gave the expected product 2h in 98 %i solated yield.…”