References
- Meyers , A. I. , Temple , D. L. , Haidukewych , D. and Mihelich , E. D. 1974 . J. Org. Chem. , 39 : 2787
- Meyers , A. I. and Mihelich , E. 1976 . Angew. Chem. Int. Ed. Engl. , 15 : 270
- Vorbruggen , H. and Krolikiewicz , K. 1981 . Tetrahedron Lett. , 22 : 4471
- Phillips , A. P. and Baltzly , R. 1947 . J. Amer. Chem. Soc. , 69 : 200
- Roush , D. M. and Patel , M. M. 1985 . Syn. Comm. , 15 : 675 The procedure we used to effect closure of the amide alcohols into oxazolines in the two examples containing acetals was a modified version of the method published by Roush: We found higher yields were obtained when 2 equivalents of both triphenylphosphine and DEAD were used: N-(1,1-dimethyl-2-hydroxyethyl) 4′-dimethoxymethylbenzamide (2.68g, 0.01 mole, 1 eq.) and triphenyl phosphine (5.24g, 0.02 mole, 2 eq.) were dissolved in THF (20 ml). The solution was cooled in an ice-bath, diethyl azododicarboxylate (3.48g, 0.02 mole, 2 eq.) was added into the solution dropwise. This was stirred for 30 minutes in the ice-bath then allowed to warm to room temperature overnight. GC-MS showed that the reaction had gone to completion. Water was added to the solution and the mixture was extracted with hexane 3 times, the organic layers were combined, dried over sodium sulfate and the solvent removed in vacuo to give 2.91 g oil. Flash chromatography on silica gel using 20% EtOAc/hexane as eluant was performed on 0.89 g of crude oil resulting in 0.65 g analytically pure product after vacuum drying (70%). The same procedure was applied to N-(1,1-dimethyl-2-hydroxyethyl) dimethoxyacetamide resulting in a 32% yield of oxazoline
- Wenkert , E. and Goodwin , T. E. 1977 . Syn. Comm. , 7 ( 6 ) : 409 Methyl 4-formylbenzoate was acetalized using trimethyl orthoformate according to a procedure described by Wenkert:
- Combret , J.-C. , Tekin , J. and Postaire , D. 1984 . Bull. Soc. Chim. Fr. , : II The oxazoline derived from methyl dimethoxyacetate had previously been synthesized from dichloroacetic acid: