The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Chemistry of vitamin E. XL. Synthesis and properties of 2-isopropyl-4,6,7-trimethyl-5-hydroxycoumaran》. Authors are Smith, Lee Irvin; King, John A..The article about the compound:2,6-Dimethyl-3,5-heptanedionecas:18362-64-6,SMILESS:CC(C)C(CC(C(C)C)=O)=O).Synthetic Route of C9H16O2. Through the article, more information about this compound (cas:18362-64-6) is conveyed.
cf. C. A. 36, 4120.3. (Me2CHCO)2CH2 (I), orange-red oil, b3 62-3°, results in 28% yield from the Na derivative of iso-PrCO2Et and iso-PrAc. I (16.85 g.), slowly added (15 min.) to 7.34 g. EtONa in 50 cc. dry EtOH at a temperature below 25°, followed by 16 g. trimethylquinone in 50 cc. dry EtOH during 1 hr., with stirring for 45 min., and acidification at 0°, gives 76% of 2,6-dimethyl-4-(2,5-dihydroxy-3,4,6-trimethylphenyl)-3,5-heptanedione (II), m. 135-5.5°. Solution of II in Ac2O and a drop of concentrated H2SO4 and immediate addition to ice give 3-methyl-1-(2-isobutyroxy-5-acetoxy-3,4,6-trimethylphenyl)-2-butanone, m. 113°. II (11.4 g.), refluxed 3 hrs. with 250 cc. HCl and 10 cc. EtOH, diluted with 500 cc. H2O and distilled with steam, gives 4.9 g. of unchanged II (not volatile with steam) and 4 g. of 2-isopropyl-4,6,7-trimethyl-5-hydroxycoumarone (III), m. 118°; this also results from the diester and HCl; 5-Ac derivative, m. 69-70°. Catalytic reduction (Raney Ni) of 2.5 g. of III (1 hr. at 125° and 1300 lb. pressure) gives 2.4 g. of 2-isopropyl-4,6,7-trimethyl-5-hydroxycoumaran (IV), m. 112°; Ac derivative, m. 72-3°. Oxidation of IV with AuCl3 or FeCl, in aqueous EtOH gives 2,3,5-trimethyl-6-(2-hydroxy-3-methylbutyl)-1,4-benzoquinone (V), a yellow or orange oil which could not be crystallized Reduction of V with Na hydrosulfite or with Zn and AcOH gives IV; the intermediate hydroquinone could not be isolated and none of the isomeric chroman is obtained. These results show that the cyclodehydration of a hydroquinone ortho substituted by a side chain containing a secondary alkyl group and a H group in the β-position involves direct elimination of H2O between the 2 HO groups and does not involve a preliminary dehydration of the side chain. Moreover, cyclization of this substituted hydroquinone occurs with such great ease that the hydroquinone cannot be isolated when the quinone is reduced.
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Reference:
Thiazole | C3H3NS – PubChem,
Thiazole | chemical compound | Britannica