2-Acetylbutyrolactone
2-Acetylbutyrolactone (ABL) is a derivative of γ-butyrolactone that is used as a precursor in organic synthesis, and it is used to identify primary amines through chemical fluorescence. Preparation 
2-Acetylbutyrolactone can be prepared by a condensation reaction between an ester of acetic acid (such as ethyl acetate) with butyrolactone in an alkaline solution. 2-Acetylbutyrolactone can also be prepared by reacting ethylene oxide with ethyl acetoacetate in alkaline conditions. Uses

Spectrofluorimetry 

2-Acetylbutyrolactone itself is only slightly fluorescent, but its derivatives show high UV fluorescence. The carbonyl group readily reacts with amines to form Schiff bases. It is for this reason that 2-acetylbutyrolactone is frequently used to confirm the creation of amines during organic synthesis. 2-Acetylbutyrolactone can also undergo a Japp‐Klingemann reaction to form fluorescent molecules with arylamines. Drug precursor 
Uses of 2-Acetylbutyrolactone also includes synthesis of:
Risperidone
Ritanserin 
Paliperidone
Ocaperidone
Seganserin
Setoperone
Metrenperone
Pirenperone
Novoldiamine (1-Diethylamino-4-aminopentane) [140-80-7]
Clomethiazole
Barmastine
R 59-022 [93076-89-2]
ID-4708 [42048-72-6]. Santalene
α-methylene-γ-butyrolactones. References 

Tetrahydrofurans