Introduction

As the supply of GBL quickly diminishes, the desire to find a synthesis of GBL from tetrahydrofuran (THF) increases.

Just to make this a more thorough study, here are a few more ref's for a few more procedures worth looking at. I think you'll like them; the oxidation of THF into butyrloactone is a classic, and is the basis of a huge number of studies. Enjoy. Gratis a Beilstein magnificum.

Reactant tetrahydrofuran (BRN 102391)
Product dihydro-furan-2-one (BRN 105248)

Reaction 1 (sodium bromate)

Reagent: aqueous sodium bromate
Catalyst: 47% hydrobromic acid
Solvent: CH2Cl2
Time: 5 hours
Temperature: 35 C
Yield 67%
Ref. 1 5934286; Journal; Kajigaeshi, Shoji; Nakagawa, Takashi; Nagasaki, Noritaka; Yamasaki, Hiromochi; Fujisaki, Shizuo; BCSJA8; Bull.Chem.Soc.Jpn.; EN; 59; 3; 1986; 747-750;

Reaction 2 (sodium bromate)

Reagent: NaBrO3, NaHSO3
Solvent: H2O
Time: 16.25 hours
Temperature: 20 C
Yield 68%
Ref. 1 6148927; Journal; Sakaguchi, Satoshi; Kikuchi, Daisuke; Ishii, Yasutaka; BCSJA8; Bull.Chem.Soc.Jpn.; EN; 70; 10; 1997; 2561 - 2566;

Reaction 3 (calcium hypochlorite)

Reagent: Ca(OCl)2
Solvent: acetic acid, acetonitrile, H2O
Time: 1 hour
Temperature: 0 C
Yield 68%
Ref. 1 5554344; Journal; Nwaukwa, Stephen O.; Keehn, Philip M.; TELEAY; Tetrahedron Lett.; EN; 23; 1982; 35-38;

Reaction 4 (nitric acid)

Reagent: aqueous HNO3
Solvent: benzene
Temperature: 25 C
Ref. 1 605467; Journal; Moschkin; Trudy Sovesc. Vopr. Ispolz. Pentozan. Syria Riga; 1955; 225, 244; Chem.Abstr.; 1959; 15048;

Reaction 5 (palladium/oxygen)

Reagent: CO2-O2, HCl
Catalyst: PdCl2-CuCl2
Temperature: 25 C
Pressure: 24 atm
Ref. 1 5737035; Journal; El'man, A. R.; Slivinskii, E. V.; Loktev, S. M.; BACCAT; Bull.Acad.Sci.USSR Div.Chem.Sci.(Engl.Transl.); EN; 37; 1988; 1969; IASKA6; Izv.Akad.Nauk SSSR Ser.Khim.; RU; 9; 1988; 2188-2189;

Reaction 5 (titanium/hydrogen peroxide)

Reagent: TS-1 (titanium silicate), 30% H2O2
Time: 12 hours
Temperature 70 C
Yield 55%
Ref. 1 5994917; Journal; Sasidharan, M.; Suresh, S.; Sudalai, A.; TELEAY; Tetrahedron Lett.; EN; 36; 49; 1995; 9071-9072; Note: FeCl2/H2O2 will work as well

Reaction 6 (H3PO5)

Reagent: H3PO5
Time: 2 hours
Temperature: 25 C
MeCN, p-benzoquinone; other ethers
Yield 34%
Ref. 1 5561643; Journal; Ogata, Yoshiro; Tomizawa, Kohtaro; Ikeda, Toshiyuki; JOCEAH; J.Org.Chem.; EN; 45; 7; 1980; 1320-1322;

Reaction 7 (H3PO5)

H3PO5
Time: 2 hours
Temperature: 25 C
Yield 34%
Ref. 1 5561643; Journal; Ogata, Yoshiro; Tomizawa, Kohtaro; Ikeda, Toshiyuki; JOCEAH; J.Org.Chem.; EN; 45; 7; 1980; 1320-1322;

Reaction 8 (copper chromite)

water, hydrogen
Temperature: 280 C
Pressure: 193 atm
beim Behandeln mit einem Kupferoxid-Chromoxid-Katalysator
Ref. 1 605466; Patent; BASF; DE 849104; 1950; DRP/DRBP Org.Chem.; DE; GE;

Reaction 9 (manganese(VII) oxide)

Reagent: Mn2O7
Solvent: CCl4, acetone
Temperature: -45 C
Yield 86%
Ref. 1 5689808; Journal; Troemel, Martin; Russ, Manuel; ANCEAD; Angew.Chem.; GE; 99; 10; 1987; 1037-1038;

Reaction 10 (zinc permanganate)

Reagent: Zn(MnO4)2/SiO2
Solvent: CH2Cl2
Time: 0.25 hours
Temperature: 20 C
Yield 51%
Ref. 1 5738472; Journal; Wolfe, Saul; Ingold, Christopher F.; JACSAT; J.Amer.Chem.Soc.; EN; 105; 26; 1983; 7755-7757;

Reaction 11 (zinc dichromate)

Reagent: ZnCr2O7*3H2O
Solvent: CH2Cl2
Time: 1 hour
Ambient temperature
Yield 70%
Ref. 1 5572812; Journal; Firouzabadi, H.; Sardarian, A. R.; Moosavipour, H.; Afshari, G. M.; SYNTBF; Synthesis; EN; 4; 1986; 285-288;

Reaction 12

Reagent: benzyltrimethylammonium tribromide, Na2HPO4
Solvent: H2O
Time: 10 hour(s)
Temperature: 60 C
Yield 67%
Ref. 1 5936936; Journal; Kajigaeshi, Shoji; Kawamukai, Hiroshi; Fujisaki, Shizuo; BCSJA8; Bull.Chem.Soc.Jpn.; EN; 62; 8; 1989; 2585-2588;

Reaction 13 (N-hydroxyphthalimide)

Yield 11%
Reagent: N-hydroxyphthalimide
Solvent: pyridine
anodic oxidation
Ref. 1 5669238; Journal; Masui, Masaichiro; Hara, Seijiro; Ueshima, Takahiro; Kawaguchi, Tetsuo; Ozaki, Shigeko; CPBTAL; Chem.Pharm.Bull.; EN; 31; 11; 1983; 4209-4212;

Reaction 14 (benzil/oxygen)

Reagent: benzil, oxygen
Time 6 hours
Temperature: 0 C
Irradiation
Note 1 Yield given
Ref. 1 6045199; Journal; Seto, Hideharu; Yoshida, Keigo; Yoshida, Shigeo; Shimizu, Takeshi; Seki, Hiroshi; Hoshino, Mikio; TELEAY; Tetrahedron Lett.; EN; 37; 24; 1996; 4179-4182;

Reaction 15 (exotic cobalt reagent)

Reagent: O2, tris(acetylacetonato)Co(III), 2,3-butanedione
Time: 6 hours
Temperature: 50 C
Pressure: 1 atm
Yield 60%
Ref. 1 5849077; Journal; Hata, Eiichiro; Takai, Toshihiro; Mukaiyama, Teruaki; CMLTAG; Chem.Lett.; EN; 9; 1993; 1513-1516;

Reaction 16 (exotic cobalt reagent)

tris(acetyloacetonato)Co(III), O2, 2,3-butanedione
Time: 6 hours
Temperature: 50 C
Pressure: 1 atm
Yield 60%
other tetrahydrofuranes; var. alpha-diketones; also with Co(II), Fe(III), Ni(II) acetylacetonates
Ref. 1 5849077; Journal; Hata, Eiichiro; Takai, Toshihiro; Mukaiyama, Teruaki; CMLTAG; Chem.Lett.; EN; 9; 1993; 1513-1516;

Reaction 17 (ruthenium (VIII) oxide)

Reagent: RuO4
Solvent: CCl4
Time: 24 hours
Ambient temperature
Yield 65%
Ref. 1 5772763; Journal; Smith, Amos B.; Scarborough, Robert M.; SYNCAV; Synth.Commun.; EN; 10; 3; 1980; 205-212;

Reaction 18 (exotic ruthenium reagent)

trans-<Ru%VI&(N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)propylenediamine)O2><ClO4>2
Solvent: acetonitrile
Time: 1 hour
Temperature: 25 C
Yield 98%
Ref. 1 5541107; Journal; Che, Chi-Ming; Tang, Wai-Tong; Li, Chi-Keung; JCDTBI; J.Chem.Soc.Dalton Trans.; EN; 12; 1990; 3735-3739;

Reaction 19 (exotic ruthenium reagent)

Reagent: <Ru%V&L(O)>%2+& <HL = <2-hydroxy-2-(pyridyl)ethyl>bis<2-(2-pyridyl)ethyl>amine>
Solvent: HClO4
Temperature: 24.9 C
Ref. 1 5582759; Journal; Che, Chi-Ming; Ho, Clare; Lau, Tai-Chu; JCDTBI; J.Chem.Soc.Dalton Trans.; EN; 5; 1991; 1259-1263;

Reaction 20 (exotic ruthenium reagent)

Reagent: <Ru%V&L(O)>%2+&-complex <HL = <2-hydroxy-2-(2-pyridyl)ethyl>bis<2-(2-pyridyl)ethyl>amine>
Solvent: acetonitrile
Yield 80%
Ref. 1 5582759; Journal; Che, Chi-Ming; Ho, Clare; Lau, Tai-Chu; JCDTBI; J.Chem.Soc.Dalton Trans.; EN; 5; 1991; 1259-1263;

Reaction 21 (exotic ruthenium reagent)

aq. t-BuOOH
Catalyst: trans-<Ru(H2O)2(bipy)2><PF6>2*H2O
Solvent: benzene
Time: 5 hours
Ambient temperature
Yield 33%
Ref. 1 6009471; Journal; Bailey, Alan J.; Griffith, William P.; Savage, Paul D.; JCDTBI; J.Chem.Soc.Dalton Trans.; EN; 21; 1995; 3537-3542;

Reaction 22 (exotic Ruthenium reagent)

Reagent: trans-<Ru(VI)(dmpipy)2O2><ClO4>2
Solvent: acetonitrile
Time: 4 hours
Ambient temperature
Yield 85%
Ref. 1 5538120; Journal; Che, Chi-Ming; Leung, Wai-Ho; Li, Chi-Keung; Poon, Chung-Kwong; JCDTBI; J.Chem.Soc.Dalton Trans.; EN; 3; 1991; 379-384;

Reaction 23 (exotic Ruthenium reagent)

Reagent: cis-<Ru%VI&(6,6'-Cl2bpy)2O2><ClO4>
Solvent: acetonitrile
Time: 90 min
Temperature: 25 C
Yield 41%
Ref. 1 5911524; Journal; Che, Chi-Ming; Leung, Wai-Ho; JCCCAT; J.Chem.Soc.Chem.Commun.; EN; 18; 1987; 1376-1377;

Reaction 24 (exotic Ruthenium reagent)

Reagent: H2O, trans-<RuL%1&O2>%2+& (L%1& = 6,7,14,15,16,17,18,19-octahydro-14,18-dimethyl-13H-dibenzo<e,n><1,4,8,12>dioxadiazacyclopentadecine
Solvent: trifluoroacetic acid
Temperature: 24.9 C
Ref. 1 5600408; Journal; Che, Chi-Ming; Tang, Wai-Tong; Wong, Kwok-Yin; Li, Chi-Keung; JCDTBI; J.Chem.Soc.Dalton Trans.;

Reverend Drone