Abstract A comparison is made of thiols with amines in their mode of reaction with different substituted 2-halomethylquinazoline 3-oxides. Whereas the reaction of some amines (particularly small primary ones), as has long been known, leads to ring-enlarging rearrangement under certain conditions, all thiol nucleophiles we have observed, ranging from small to large, lead without rearrangement to direct benzylic substitution only. ...