4-Isopropyl-2-oxazolin-5-one

Two further preparations of 3-nitropropanal 1 have been claimed in the literature by treatment of 1-chloro-3-nitro-2-propanol with potassium hydroxide,5 and by reaction of the 4-isopropyl-2-oxazolin-5-one anion with nitroethene.6 These alternate methods are less suited and less economic for the preparation of 3-nitropropanal 1 on a multigram scale. 

A. Barco, S. Benetti, C. De Risi, G. P. Pollini, G. Spalluto, and V. Zanirato, 4-Isopropyl-2-oxazolin-5-one anion as a new convenient formyl anion equivalent for conjugate addition and aldol reactions. Tetrahedron Lett. 34 3907 (1993). 

Tetroses and Pentoses - 4-0- -Butyldimethylsilyl-2,3-0-isopropylidene-L-threose (1) has been prepared in seven efficient steps from o-xylose. 3,4-0-Isopropylidene-D-eythrulose (4) has been synthesized from the known tetritol derivative 2 by primary protection as the silyl ether 3, followed by Dess-Martin oxidation and desilylation. Compound 2 was derived from D-isoascorbic acid (see Vol. 22, p. 178, refs. 9,10). In a similar reaction sequence, the enantiomer 5 has been obtained from L-ascorbic acid. The dehomologation of several di-0-isopropylidenehexofuranoses e.g., 6- 7) has been carried out in two steps without intermediate purification, by successive treatment with periodic acid in ethyl acetate, followed by sodium borohydride in ethanol. Selective reduction of 3-deoxy-D-g/jcero-pentos-2-ulose (8) to 3-deoxy-D-g/> cero-pent-2-ose (9) has been achieved enzymically with aldose reductase and NADPH." 4-Isopropyl-2-oxazolin-5-one (10) is a masked formaldehyde equivalent that is easily converted to an anion and demasked by mild acid hydrolysis. One of the three examples of its use in the synthesis of monosaccharides is shown in Scheme 1. ... 

Trifluoromethyl-4-isopropyl-3-oxazolin-5-one (45) reacts with aryl-thioesters of arylsulfonic acids to yield derivatives which, on heating, give benzothiazines116 [Eq. (22). With arylsulfenyl chlorides, 2-... 

Isopropyl-4 linalyl-2-phenyl-2-oxazolin-5-one refluxed 3 hrs. in benzene 2-geranyl-4 isopropyl-2-phenyl-3-oxazolin-5-one. Y ca. 100%. F. e. s. B. Kubel, G. Hbfle, aid W. Steglidi, Ang. Ch. 87, 64 (1975). 

Pyrazines have been prepared by heating 1,2-dicarbonyl compounds with a-amino acids. Thus Rizzi (308) observed that under the conditions of the Strecker degradation, equimolar amounts of DL-valine (44) and butane-2,3-dione in refluxing bis(2-methoxyethyl) ether, diglyme, gave isobutyraldehyde, tetra-methylpyrazine (9%), and a mixture of cis- and trans-2-isopropyl-4,5-dimethyl-3-oxazoline (4%). He proposed a reductive amination mechanism in which butane-23-dione was converted to 2-aminobutan-3-one which underwent self-condensation to the pyrazine. Tetramethylpyrazine was also prepared when the same reactants were heated in dimethylformamide at 123° for 5 hours (and other pyrazines prepared similarly) (308a). 

Hubert and co-workers have reported that alkyl diazoacetates react with A -diisopropylcarbodiimide in the presence of transition metal salts to give 2-isopropylimino-3-isopropyl-5-alkoxy-4-oxazolines.115 For example, treatment of ethyl diazoacetate with rhodium(II) acetate in the presence of A,A -diisopropylcarbodiimide (215) produced 2-iso-propylimino-3-isopropyl-5-ethoxy-4-oxazoline (217) in good yield. The formation of oxazoline 217 was interpreted in terms of an addition of ethoxycarbonylcarbene onto one of the nitrogen atoms of the carbodi-imide to give the transient ylide 216 which then cyclized to produce the observed heterocycle. 

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