2-undecyl-4H-3,1-benzoxazin-4-one (2) was prepared and reacted with primary and secondary amines affording compounds 3–7, while with hydrazine hydrate it gave the quinazolinone derivative 8. The reaction of 8 with 3,4,5-trimethoxybenzaldehyde followed by thioglycollic acid yielded 9 and 10, respectively. Acylation of 8 using cinnamoyl chloride gave 11. Furthermore, treatment of 2 with hydrazine derivatives provided 12 and 13. Fusion of 2 with ammonium acetate gave the quinazolinone derivative 14 which upon treatment with ethyl chloroacetate yielded the ester 15. The hydrazide 17 was obtained from hydrazinolysis of the ester 15.