5- Amino-3,4-dimethyl-1,2-oxazole

Dimethoxybenzoyl chloride Benzoyl chloride, 2,3-dimethoxy- (9) (7169-06-4) 2-Amino-2-methyl-1-propanol 1-Propanol, 2-amino-2-methyl- (8,9) (124-68-5) 2,2 -Dimethoxy-6-(4 ,4 -dimethyloxazolinyl)biphenyl Oxazole, 2-(2 ,6-dimethoxy[1,1-biphenyl]-2-yl)-4,5-dihydro-4,4-dimethyl- (9) (57698-39-7)... 

Conceptually interesting is the synthesis of the oxazole system 94 through a Beckmann rearrangement of a-formyl ketoxime dimethyl acetals 93 which demonstrated the possibility of a non-amino acid pathway in the biosynthesis of marine derived oxazoles <06CC1742>. 

The rhodium acetate complex catalyzed the intramolecular C-H insertion of (/ )-diazo-fR)-(phenylsulfonyl)acet-amides 359 derived from (f )-amino acids to afford in high yield the 6-benzenesulfonyl-3,3-dimethyl-7-phenyl-tetrahydro-pyrrolo[l,2-c]oxazol-5-one 360 (Equation 63) <2002JOC6582, 2005TL143>. 

The configurations of the binaphthyl products have been established by conversion to compounds of known absolute configuration. Thus, (5 )-2-(l,l-binaphthyl-2-yl)-4,5-dihydro-4,4-dimethyl-l,3-oxazole was transformed into (S)-2-amino-l, 1-binaphthyl30 31 and the (S)-2-... 

Amino-carboxy-methyl )-2-methyl-. [bzw. -2,4-dimethyl-... bzw. 2-methyl-4-phenyl-...]-/, 2-oxazol (X = H, CH CSHS)... 

Intramolekularer Ersatz einer Methoxy-Gruppe durch eine Amino-Gruppe erfolgt bei der Einwirkung von Lithium-diisopropylamid auf 2-[3-(co-Amino-alkyl)-2-methoxy-phe-nyl]-4,4-dimethyl-4,5-dihydro-l,3-oxazol in Tetrahydrofuran. Auf diese Weise lassen sich erhalten4 ... 

Enolizable ketones were converted directly into their a-hydroxy dimethyl acetals upon reaction with DIB and methanolic potassium hydroxide at room temperature. If, during work up, there was acid treatment, then a-hydroxyketones were directly obtained. Numerous examples are known for such transformation, e.g. with 3-pentanone, acetophenones, 2,6-diacetylpyridine [16], tropan-3-one [17], -amino-ketones of great structural variety [18], etc. even a free radical reacted successfully in this way [19]. This conversion for an acetyl-oxazole served for the preparation of pyrimidine derivatives. 

Furan 2-Aminomethyl-5-(2,4-dioxo-1,2,3,4-tetrahydro-pyrimidino)-2,5-dihydro- IV/lc, 578 Imidazo(l,2-a]pyridin 1,5-Dimethyl-8-nitro-7-oxo-l,2,3,7-tetrahydro-E15/3, 2790 [cycl. (R2N)2C = CH-N02 4- Diketen] 1,3-Oxazol 4-Cyan-5-(diethoxy-methylen-amino)- E4, 565 (Het — NH2 + Orthoester) Pyrazin 3-Amino-2-methoxycarbo-nyl-5-propanoyl- E9b/2, 324 (H - CO-R)... 

Oxazol 4-Carboxy-5-dimethyl-amino-2-(4-nitro-phenyl)- E8a, 932 (4-CO —CF3 - 4-COOH)... 

Commercially available dimethyl cyclopropylmalonate 30 was converted to mono ester 31 by careful saponification using sodium hydroxide. Coupling with l-amino-2-hexanol afforded the hydroxyamide 32 which was oxidized to ketone 33 under Swern conditions. Condensation to oxazole 34 was effectively achieved by utilizing a two-phase system consisting of dichloromethane and sulfuric acid. Reaction with deprotonated dimethyl methylphosphonate gave the 0-ketophosphonate 35 in an excellent overall yield. 

Carboxy groups may be protected by reaction with 2-amino-2-methylpropanol the resulting 4,4-dimethyl-4,5-dihydro-l,3-oxazol is inert to organomagnesium halide reagents and can be removed by acid treatment ... 

Ahnlich der Reaktion von 3(5)-Amino-lH-pyrazolen mit 3-Oxo-alkansaure-estern verlauft die Umsetzung mit 4-ChLorcarbonyl-3,5-dimethyl-l,2-oxazolen als Dicarbonyl-Aquivalent. Nach Acylierung des 3(5)-Amino-lH-pyrazols und Offnung des 1,2-Oxazol-Rings werden 6-Acetyl-5-hydroxy-7-methyl-[Pg.682]

Bei der Bestrahlung von 3,5-Dimethyl- benzo-[c]-l,2-oxazol)/Schwefelsaure erhalt man u. a. neben 6-Amino-3-hydroxymethyl-acetophenon (13% d.Th.) 28% 6-Amino-3-hydroxy-2-rnethyl-acetophenon (Mechanismus s. Lit.). 

Various preparation methods have been described. Wiley (1945, 1947) converted a-amino acids to acetdmido ketones by reaction with acetic anhydride in pyridine and obtained 2,5-dimethyl-4-substituted oxazoles after dehydration of the enol form of the intermediate. Theilig (1953) applied the reaction of a-bromoketones with the appropriate amides. 

N,5R,6R)-6-[[3-(2,6-Dichlorophenyl)-5-methyl-l,2-oxazole-4-carbonyl] amino] -3,3 -dimethyl-7-oxo-4-thia-1 -azabicyclo [3.2.0] heptane-2-carboxylic acid... 

The fused oxazole derivative 100 was synthesized from 3-azido-3-deoxy-l,2 5,6-di-O-isopropylidene-a-D-allofuranose, the key final step being the reaction of methyl 3-amino-3-deoxy-5,6-0-isopropylidene-p-D-alloside with DMF dimethyl acetal. The annelated pyranoside 101 was obtained by cyclization of a branched chain hexosulose derivative, and the fused triazole-piperidinoses such as 102 were made by a radical cyclization of a 3-pyrazolo-6-iodo-sugar derivative. The spiro-isoxazohne 103 and related isomers have been synthesized by dipolar cycloadditions of mesitonitrile oxide to 2-deoxy-2-C-methyl-ene-pentonic acids, themselves available in five steps from D-mannitol. Intra-... 

While the cycloaddition of oxazole with acetylene is a well-established method for furan synthesis [36], the corresponding reaction of 5-amino oxazole was unknown at the outset of this work. As shown in Eq. (3) of Scheme 15.19, the reaction of 24b with 3-phenyl-2-propynoyl chloridephenylpropioloyl chloride (55a) proceeded smoothly to provide the 5,6-dihydro-furo[2,3-c]pyrrol-4-one (56) in greater than 95% yield. A triple domino sequence involving acylation/intramolecular DA cycloaddition/retro DA could explain the reaction outcome. That the domino process was initiated by acylation was evidenced by the fact that 24b failed to react with dimethyl acetylenedicarboxylate (DMAD) under the identical conditions. 

Dehydroacetic acid oxime rearrangesinpolyphosphoricacidto 3-acetamid04 hydroxy-6-methyl-(2ff)-2-pyrone and 2,6-dimethyl-(4 0 Pyrano[3,4-d] oxazol-4-one (W-242). Treatment of W-242 with ammonia gives 2,6-dimethyl-(5//)-oxazolo[4,5-c]-4-pyridone, which, in turn, gives 3-acetamido4-hydroxy-6-methyl-2-pyridone with hydrochloric acid at room temperature and 3-amino-4-hydroxy-6-methyl-2-pyridone on heating. ... 

Although Rh -catalyzed reaction of dimethyl diazomalonate with nitriles to afford 1,3-oxazoles (eq 4) generally gives high yields, it is incompatible with an a-amino function. Thus, an alternative route was proposed for preparation of oxazole derivatives of a-amino acids. This method involves Rh -catalyzed insertion into N-H bond of an amide, derived from the amino acid, followed by intramolecular condensation (eq 36). ... 

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