Ring opening reactions tetrahydrofuran

Ionic ring-opening reactions of cyclopropanes under solvolytic conditions followed by ring-closure of the primarily produced cations have been employed for the synthesis of lactones, tetrahydrofuranes, and pyranes, respectively, as shown below [176]. 

Benfatti and coworkers have reported further advancements in the intramolecular ring-opening reaction of p-hydroxy epoxides affording spiro-oxetanes and tetrahydrofurans (III and IV, respectively, Fig. 24), [303]. 

A similar ring-opening reaction of tetrahydrofuran takes place only in the presence of Sml3 (equation 177)1106. 

Ring opening of tetrahydrofuran derivatives has been studied using chlorotrimethylsilane and sodium iodide 2-methyltetrahydrofuran is opened predominantly to give 5-iodopentan-2-ol but the reaction involving 3-methyltetrahy-drofuran is less selective. Lithium 4,4-di-/-butylbiphenylide has also been used to cause the ring opening of tetrahydrofuran at 80 C in the presence of boron trifluoride etherate. 

The cyclodimerization of 3,3-dimethylcyclopropene to form 3,3,6,6-tetramethyl-exo-tri-cyclo[3.1.0.0 ]hexane (4) can also be achieved with pentacarbonyliron in toluene at 95"C in 3 hours (no yield given) or in tetrahydrofuran at 60 °C with catalytic amounts of hexacarbonyl-molybdenum (77% yield, 93% conversion) or hexacarbonyltungsten (86.5% yield). With nonacarbonyldiiron a stoichiometric ring-opening reaction and formation of tricarbonyl(2-methyl-l-propenylketene)iron has been observed (see Section 2.C. for details). A 40% yield of the tricyclic dimer 4 is obtained under the catalytic action of ( / -cycloocta-l,5-diene)(t -cyclopentadienyl)cobalt(I). ... 

The susceptibility of nucleophiles to ring-opening reactions is often increased after the activated cyclopropane structure has been incorporated into a polycyclic system due to the additional strain. 3-enaqueous tetrahydrofuran. When 3-cnt/o-methoxytricyclo[3.2.0.0 ]heptan-6-one was dissolved in methanol, the corresponding ring-opened dimethoxy derivative 22 (R = Me) was isolated in high yield. 

A number of anhydro sugar derivatives have also been polymerized in ring opening reactions catalyzed by Lewis acids (iO, 34,35,67,122-130, 133,134). These reactions in contrast proceed by an activated chain polymerization like that of a vinyl monomer or more closely like that of tetrahydrofuran which proceeds by means of a propagating trialkyl-oxonium ion on the end of the growing chain (/35) (Fig. 6). 

The regioselective ring opening reactions of epoxides (eq 39), oxetanes, and tetrahydrofurans (eq 40) has been promoted by ZnCU to afford adducts with suitable nucleophiles. 

Uses. Furfural is primarily a chemical feedstock for a number of monomeric compounds and resins. One route produces furan by decarbonylation. Tetrahydrofuran is derived from furan by hydrogenation. Polytetramethylene ether glycol [25190-06-1] is manufactured from tetrahydrofuran by a ring opening polymeri2ation reaction. Another route (hydrogenation) produces furfuryl alcohol, tetrahydrofurfuryl alcohol, 2-methylfuran, and 2-methyltetrahydrofuran. A variety of proprietary synthetic resins are manufactured from furfural and/or furfuryl alcohol. Other... 

The parallel ability of oxiranes to undergo ring opening to carbonyl ylides was first noted in the case of tetracyanooxirane (68T2551), but such reactions have not been widely exploited. The addition to alkenes, leading to formation of tetrahydrofurans, is stereospecific (Scheme... 

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