Theilig, Gerhard’s team published research in Chemische Berichte in 86 | CAS: 20662-83-3

Theilig, Gerhard published the artcileFormamide reactions. II. Studies in the oxazole series and conversion of oxazoles to imidazole with formamide, Recommanded Product: 4,5-Dimethyloxazole, the publication is Chemische Berichte (1953), 96-109, database is CAplus.

Oxazoles, O.CR:N.CR’:CR” (I), are prepared from α-bromo ketones and RCO₂H or RCONH₂, from acylated aliphatic acyloins, α-acyloxy ketones, and enediol diesters and are converted into imidazoles by treatment with HCONH₂ (II). Heating AcCHBrMe (III) (38 g.) and 90 g. II 5 h. at 100° gives 21% I (R = H, R’ = R” = Me), b₁₃ 35-65°, b₇₆₀ 128-33°; PhCOCHBrPh and II 3 h. at 120-40° give 41% I (R = H, R’ = R” = Ph), b₁₄ 190-4°; PhCOCH₂Br and PrCONH₂ (IV) 3 h. at 140° give 15% I (R = Pr, R’ = Ph, R” = H), b₁₂ 148-52°; III and AcNH₂ 2.5 h. at 110° give 67% I (R = R’ = R” = Me) (V), b₂₀ 42-8°; III and IV give 36% I (R = Pr, R’ = R” = Me), b. 175-85°; PrCOCHBrEt and IV 1 h. give 70% I (R = R’ = Pr, R” = Et), b₁₃ 95-8°. Refluxing 29 g. EtCOCHEtOAc (VI) in 100 cc. AcOH 1 h. with 50 g. AcONH₄ gives 82% I (R = Me, R’ = R” = Et), b₁₇ 64-5°; 12 g. VI refluxed with 22 g. EtCO₂NH₄ and 70 cc. EtCO₂H 1.25 h. gives 80% I (R = R’ = R” = Et), b₉ 62-4°; 15 g. PrCOCHPrOAc refluxed 1 h. with 80 cc. AcOH and 30 g. AcONH₄ gives 85% I (R = Me, R’ = R” = Pr), b₁₀ 82-4°; 10 g. Me₂CHCOCH(OAc)CHMe₂ refluxed 1 h. with 50 cc. AcOH and 20 g. AcONH₄ gives 67% I (R = Me, R’ = R” = Me₂CH), b₁₂ 62-72°, which gives a crystalline HgCl₂ salt. Dissolving PhCOCHPhOH in PrCOCl at 40° and heating the mixture on the water bath give PhCOCHPhO₂CPr, m. 63°, which (11 g.), refluxed with 40 cc. PrCO₂H and 3 g. NH₃ 1.5 h., gives 4.5 g. I (R = Pr, R’ = R” = Ph), b₁₂ 220-2°, m. 69°, and 4 g. 2-propyl-4,5-di-phenylimidazole, m. 206°. Refluxing 36 g. BzCHPhO₂CCH₂CHMe₂ in 100 cc. AcOH with 45 g. AcONH₄ gives 60% I (R = Me₂CHCH₂, R’ = R” = Ph), b_0.4 182°; refluxing 22 g. benzoin heptanoate in 100 cc. AcOH 1.5 h. with 40 g. AcONH₄ gives 29% I (R = C₆H₁₃, R’ = R” = Ph), b_0.01 160-3°. Refluxing 15 g. BzCHEtOAc, 75 cc. AcOH, and 30 g. AcONH₄ 1 h. gives 50% I (R = Me, R’ = Ph, R” = Et), b₁₀ 133-5°; similarly, p-MeC₆H₄COCH(OAc)CHMe₂ gives 50% I (R = Me, R’ = p-MeC₆H₄, R” = Me₂CH), b₁₀ 149-51°. Refluxing 32 g. PhCOCHBrEt, 27 g. EtCO₂Na, and 60 g. EtCO₂H 2 h. gives 55% I (R = R” = Et, R’ = Ph), b₁₀ 139-44°, and some 2,5-diethyl-4-phenylimidazole, m. 143-4°. Refluxing 25.5 g. BzCHBrCHMe₂, 17 g. AcONa, and 85 cc. AcOH 2 h., filtering the mixture, and refluxing the filtrate with 40 g. AcONH₄ 1.5 h. give 82% I (R = Me, R’ = Ph, R” = Me₂CHCH₂), b₁₀ 143-5°; similarly, 21 g. BzCHBrMe (VII), 19 g. EtCO₂Na, 80 cc. EtCO₂H, and 30 g. EtCO₂NH₄ give 62% I (R = Et, R’ = Ph, R” = Me), b₉ 131-3°; 22 g. VII, 25 g. PrCO₂Na, and 80 cc. PrCO₂H 2 h. give 31% I (R = Pr, R’ = Ph, R” = Me), b₁₀ 154-6°; 27 g. BzCH₂Br, 30 g. PrCO₂Na, 100 cc. PrCO₂H, and 5.5 g. NH₃ in 50 cc. PrCO₂H give 6% I (R = Pr, R’ = Ph, R” =H), b₁₂ 148-52°; 43 g. VII, 30 g. AcONa, 50 cc. AcOH, and 30 g. AcONH₄ give 66% I (R = R” = Me, R’ = Ph), b₁₂ 136-8°; 28 g. BzCHBrEt, 20 g. AcONa, 50 cc. AcOH, and 20 g. AcONH₄ give 65% I (R = Me, R’ = Ph, R” = Et), b₁₂ 146-8°. Adding 5 cc. EtCOCl to 13 g. powd. Na in 500 cc. boiling ether and, when the reaction has started, adding another 41 g. EtCOCl give 58% 3-hexene-3,4-diodipropionate (dipropionyl) (VIII), b₁₄ 119-21°; 4-octenel 4,5-diol dibutyrate (dibutyryl), 62%, b₁₆ 123-9°, and 2,7-dimethyl-4-octene-4,5-diol diisovalerate (diisovaleryl), 77%, b₁₂ 157-66°, are prepared similarly. Refluxing 8.5 g. VIII with 50 cc. AcOH and 15 g. AcONH₄ 1 h. gives 63% I (R = R’ = R” = Et), b₁₂ 72-3°; I (R = R’ = R” = Pr), 61%, b₁₇ 116-19°; I (R = R’ = R” = Bu), 72%, b₁₃ 120-3°. A mixture of 50 cc. anhydrous HCO₂H and 50 cc. Ac₂O (ice-cooled) is kept with 20 g. benzoin 3 days at 20° and poured into 600 cc. H₂O, giving 79% benzoin formate which (18 g.) is refluxed with 8 g. NH₃ in 100 cc. HCO₂H 1 h. and poured into 300 cc. H₂O, giving 72% I (R = H, R’ = R” = Ph), b₁₁, 188-92°; warming 2 g. PhCH(OH)CONHCH₂OH with 10 cc. POCl₃ 0.5 h. at 65-70° and distilling off the excess POCl₃ in vacuo give 17% I (R = R’ = H, R” = Ph), m. 39-40°. Refluxing 4 g. 4-phenyloxazole with 50 cc. HCONH₂ 3 h. gives 97% 4(or 5)-phenylimidazole, m. 128°. The following HN.CR:N.CR’:CR” (IX) are prepared similarly from the corresponding I: 2-methyl-4(or 5)-Ph 88%, m. 161°; 4,5-di-Me, 70%, m. 117°; 2-methyl-4,5-diphenyl, 85%, m. 241°; 2-Pr homolog, 82%, m. 206°; 2,4,5-tri-Me, 33%, m. 128-30°; 2-methyl-5(or 4)-ethyl-4(or 5)-phenyl-, 90%, HCl salt m. 127°; 2-methyl-5(or 4)-isobutyl-4(or 5)-phenyl-, 29%, HCl salt, needles, m. 194-6°; 5(or 4)-methyl-2-ethyl-4(or 5)-phenyl-, 17%, HCl salt m. 198-200°. On treating the appropriate I with a 0.5% solution of 2,4-(O₂N)₂C₆H₃NHNH₂ in 2N HCl, I are cleaved, giving the following RCONHCHR’CR”:NNHC₆H₃(NO₂)₂-2,4 (all are needles, R, R’, R”, color, % yield, m.p. in the order given): H, Ph, H, 87, yellow-orange, 243-4°; Me, Ph, H, 76, yellow-orange, 233-5°; H, Me, Me, 71, yellow-orange, 222-3°; Me, Me, Me, 73, yellow, 304-7°; Me, Et, Et, 47, orange-red, 277-8°; Et, Et, Et, 22, red, 259-61°. Adding alternately in small portions 35 cc. 10% NaOH and 5 g. BzCl to 2 g. 4,5-dimethyloxazole, stirring the mixture 0.5 h., and extracting with C₆H₆give 71% MeCOCHMeNHBz, fine needles, m. 64-5° (2,4-dinitrophenylhydrazone, m. 199°). The mechanisms of these reactions are briefly discussed.

Chemische Berichte published new progress about 20662-83-3. 20662-83-3 belongs to oxazolidine, auxiliary class Oxazole, name is 4,5-Dimethyloxazole, and the molecular formula is C13H15NO6S, Recommanded Product: 4,5-Dimethyloxazole.

Referemce:
https://en.wikipedia.org/wiki/Oxazolidine,
Oxazolidine | C3H7NO – PubChem