Piperazinone derivatives, such as compound 4, are being

Chapter 23, Problem 23.93

(choose chapter or problem)

Piperazinone derivatives, such as compound 4, are being investigated for their potential use in the treatment of migraines as well as a variety of other diseases, including hypertension and sepsis. The following two-step synthetic procedure was developed as a general method for producing a variety of piperazinone derivatives (Tetrahedron Lett. 2009, 50, 38173819). Compound 1 is a readily available starting material that can be converted to compound 2 via an SN2 process. Reductive amination of compound 2 affords compound 3 which is short-lived and rapidly undergoes acid-catalyzed amide formation to the cyclic product 4, a piperazinone derivative. O Br H2N O N PhCH2NH2 NaBH3CN AcOH, heat 1 NaHCO3 DMF 2 H 4 3 OMe O OMe O (a) Draw the structure of 3 and explain why it is produced as a diastereomeric mixture. (b) Draw the structure of 4 and determine whether it will be produced as a mixture of diastereomers. Explain your reasoning.