The Cyclization of Propynyl Carbanilates to 2-Oxazolidones

Attempted synthesis of a keto diazene: reactions of propargylic amines, sulfamides, and ureas

“…A reaction sequence explaining the recovery of starting material is illustrated in eq 3. Isolated oxazoline 11 was converted to ester 12 under mild hydrolytic conditions and 12 was converted back to 10 by hydrolysis of the ester under more rigorous conditions. It is interesting to note that diacetone alcohol 13 (4-hydroxy-4-methyl-2-pentanone, 13) gives the normal Ritter product amide 14; undoubtedly, this reflects the difference between 10 and 13 in their respective cation stabilities.…”

“…The solution was stirred for 24 h. In rapid succession the mixture was poured over ice, rapidly neutralized with K2C03, and extracted with CHC13. The CHCI3 extract was dried (MgS04) and concentrated to give a thick yellow liquid which afforded 3.2 g (22%) of 2-methyl-3oxo-2-butyl acetate (12) with vacuum distillation: bp 28 °C/0.1 mm; NMR (CDCI3) 1.47 (s, 6 ), 2.08 (s, 3 H) and 2.11 ppm (s, 3 H); IR The crude solid which remained was recrystallized from pentane to give 2.5 g (17%) of 4,5-dihydro-2,4,5,5-tetramethyl-4-hydroxyoxazole (11) as white needles: mp 93-94 °C; NMR (CDC13) 1.27 (s, 3…”

“…Found: C, 62.65; H, 8.54; N, 12.95. Hydrolysis of l-tert-Butyl-5-methylene-4,4-dimethyl-2imidazolidinone (22a). A mixture of 0.5 g (2.8 mmol) of imidazolidinone 22a and 50 mL of 5% hydrochloric acid was stirred for 12 h at room temperature. The solution was extracted with CHC13, dried (MgS04), and concentrated, and the solid was recrystallized from hexane to give 0.2 g (36%) of N-ferf-butyl-N'-2-methyl-3-oxo-2butylurea (2c): mp 201-202 °C; NMR (CDClg) <51.32 (s, 9 ), 1.41 (s, 6 ), 2.21 (s, 3 H), 4.50 (br s, 1 H) and 5.10 ppm (br s, 1 H); IR (CHC13) 3431,1711, and 1680 cm"1.…”

Carbamates and 2-oxazolidinones from tertiary alcohols and isocyanates

“…That N-arylcarban~ates of propargyl alcohols can be cyclized to give 4-alkylidene-2-oxazolidinones is well established (3,11,12); the ilmr spectra of the products having been shown (3,12,13) to be in agreement with the structure containing a five-membered ring and an exocyclic double bond [3]. The conditions necessary for :LIZATION OF CARBAMATES 27 the reaction vary from heating to 140 "C (for R1 = R Z = H ; Ar = phenyl) to use of basic catalysts such as sodium acetate or pyridine (R1 = R2 = alkyl; Ar = dichlorophenyl) or sodiuinmethoxide (RI = R2 = alkyl; Ar = phenyl).…”

Synthesis of N-substituted-4-methylene-oxazolidinones via base-catalyzed cyclization of propargylic alcohols with p-toluenesulfonyl isocyanate

“…Consequently, there is increasing interest being paid toward the synthesis of N -substituted-4-methylene-oxazolidinones. 5–11 Most of these approaches are focused on nucleophilic cyclization via transition-metal-catalyzed strategies. However, the high catalyst loading in some of these processes results in a high economic cost.…”