The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Reactions of furan compounds. IV. High-temperature decomposition of the vapors of tetrahydrofuronitrile and Me tetrahydrofuroate to give 2,3-dihydrofuran and cyclopropanealdehyde》. Authors are Wilson, Christopher L..The article about the compound:Methyl tetrahydrofuran-2-carboxylatecas:37443-42-8,SMILESS:O=C(C1OCCC1)OC).Safety of Methyl tetrahydrofuran-2-carboxylate. Through the article, more information about this compound (cas:37443-42-8) is conveyed.
Tetrahydrofuramide (I) is not dehydrated by COCl2 at high temperatures At 360-400° over silica gel, I gives a mixture of tetrahydrofuronitrile (II) and 2,3-dihydrofuran (III), together with some HCN; the yield of II at 290° was 74%, at 310° 55%, and at 330° 40% (yields are based on consumption, see Part III); over Na phosphate (pumice impregnated with 120 g. NaH2PO4 and 15 cc. H3PO4 in 85 cc. H2O and dried by heating slowly to 300°) at 400° the yield of II was 90%, consumption of I 50-85%. With N as carrier gas (2 l./hr.), 70% of II was recovered when passed over earthenware rings at 450°; 10% was impure III. Silica gel at 500° gives 20% of tetrahydrofuran (IV)-III mixture (48% of III), 10% of unchanged II and 10% of a compound (V), which may be CH2.CH2.C:CHCN, b. 130-40°. Na phosphate at 500° gives HCN, only a little III + IV and mainly cyclopropanecarboxaldehyde (VI), b14 42-4°; 2,4-dinitrophenylhydrazone, orange-red, m. 173-5°; p-nitrophenylhydrazone, golden-yellow, m. 129-32°; dimedon derivative, m. 160-2°. NH4 tetrahydrofuroate (aqueous solution containing an excess of NH3) over earthenware rings gives an equimol. mixture of the free acid and I; over silica gel at 500-600° V and II were formed; over Na phosphate, the temperature and carrier gas (N, CO2) appeared to have little influence on the results; between 450-550° there resulted 20-30% of a product b. 45-90° containing MeOH, III, and VI; over silica gel at 375°, the products were III and PrCHO (2,4-dinitrophenylhydrazone, orange-brown, m. 120-5°); at 400°, the ester gives 30% of a liquid containing some III and VI. VI was prepared in about 20% yield from Cl(CH2)3CN and SnCl2 in ether (saturated with HCl).
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Reference:
Benzisoxazole – Wikipedia,
Benzisoxazole – an overview | ScienceDirect Topics