Synthesis of 2‐Cyanoquinazolin‐4‐ones from 3′,5′‐Dichloro‐1 H ‐spiro(quinazoline‐2,4′‐[1,2,6]thiadiazin)‐4(3 H )‐ones

(E)-4-Oxo-3,4-dihydroquinazoline-2-carbaldehyde Oxime

Reaction of 4-oxo-3,4-dihydroquinazoline-2-carbaldehyde with hydroxylamine hydrochloride (1.1 equiv) in the presence of K2CO3 (1 equiv) gave (E)-4-oxo-3,4-dihydroquinazoline-2-carbaldehyde oxime (8) in 58% yield. The compound was fully characterized and the conformation of the oxime was supported by single crystal x-ray diffractometry.

Synthesis and Chemistry of Benzo[e][1,2,6]thiadiazino[3,4-b][1,4]diazepin-10(11H)-ones and Related Ring Transformations

2-[(3,5-Dichloro-4H-1,2,6-thiadiazin-4-ylidene)amino]benzamides are cyclized to benzo[e][1,2,6]thiadiazino[3,4-b][1,4]diazepin-10(11H)-ones via (i) treatment with NaH and via (ii) Pd-catalyzed C-N coupling. The behavior of the latter toward nucleophiles and thermal, oxidative, and reductive conditions revealed unexpected transformations to 3,5-dioxo-4,5-dihydro-3H-benzo[e][1,4]diazepine-2-carbonitrile and 2-(4-substituted-1,2,5-thiadiazol-3-yl)quinazolin-4(3H)-ones.