Notes that of the betaine 5,9 and thus the former give stable y lides and the latter gives a betaine.Possibly the high acidity of the betaine in the case of the ylide lb is due to a resonance effect of the phenyl group.
Experimental SectionMaterials.-Benzoyl isocyanate was prepared according to the procedure of Speziale:10 bp 99-101°( 20 mm); ir 2240 cm-1 (NCO).The ylides la,11 4a,12 and 4b12 were prepared according to the known procedures. The physical properties were identical with reported data. Reaction of the Ylide la.-Benzoyl isocyanate (0.02 mol) dissolved in 3 ml of benzene was added dropwise to 0.02 mol of the ylide la dissolved in 200 ml of benzene under a nitrogen stream. The mixture was stirred at 50°for 3 hr. The resulting precipitate was filtered off and recrystallized with methanol to give 6.0 g (93%) of the ylide 2a:
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