NEW MATERIAL: A compound of formula I (R1 is H or methyl; R2 is C1-12 alkyl).

EXAMPLE: 2,8,14,20Tetramethylpentacyclo [19,3,1,1,13,7,19,13,115,16] octacosa1(25),3,5,7(28),9,11,13(27),15,17,19(26),21,23dodecaene4,6,10,12,16,18,22,24octa-(4-(1,3,3 a,4,7,7ahexahydro-1,3dioxo-4,7-methano2H-isoindol-2yl)benzoate.

USE: The oligomer is useful for preparing cured fibre reinforced composites with high strength and high glass transition temperature. The volatile components are not formed in the cure and the oligomer does not have voids.

PROCESS: A compound of formula II is reacted with a compound of formula III in the presence of an acid acceptor under anhydrous conditions to give the compound of formula I.