Fischer oxazole synthesis has also been useful in the synthesis of 2-(4-Bromophenyl)5-phenyloxazole starting with benzaldehyde cyanohydrin and 4-bromobenzaldehyde. However, oxazole ring chlorination occurs to give 2,5-bis(4-bromophenyl)-4-chlorooxazole 7 along with 2,5-bis(4-bromophenyl)-4-oxazolidinone 8. The latter compound is in general a by-product. Another useful example is the one pot two-step synthesis of halfordinol, a parent compound for Rutaceae alkaloids. The initial steps follow the Fischer oxazole synthesis, although the acid-catalyzed cyclization occurs in two steps rather than one, which ensures the formation of the di-chloro intermediate, preventing formation of the regioisomer. In recent research, a reconsideration of the Fischer oxazole synthesis has led to the synthesis of 2,5-disubstituted oxazoles from aldehydes and α-hydroxy-amides. However, unlike the Fischer oxazole synthesis, the new method is not limited to diaryloxazoles. References Nitrogen heterocycle forming reactions Oxygen heterocycle forming reactions Heterocycle forming reactions Name reactions Emil Fischer