The present invention provides a process for preparation of 1-[3-(dimethylamino)propyl]-1-(4-fluorophenyl)-1,3-dihydro-5-isobenzofuran carbonitrile comprising reacting a compound of formula IVa, in the presence of a base with a compound of formula RX, wherein R is selected from alkyl, alkenyl, aryl and heteroaryl which may be optionally substituted with electron withdrawing groups and X is selected from F, Cl, Br, I, CN, OTf and OR1, wherein Tf represents trifluoromethanesulfonyl group, and R1 is optionally substituted alkyl, Z is a cyano group or a group that may be converted to a cyano group; further wherein RX is selected such that an intermediate ether derivative, a compound of formula Va formed from said reaction cyclizes to a compound of formula VI, and where Z is not a cyano group, conversion of the group Z in the compound of formula VI to a cyano group to form 1-[3-(dimethylamino)propyl]-1-(4-fluorophenyl)-1,3-dihydro-5-isobenzofuran carbonitrile. The present invention also provides novel ether compound, a compound of formula Va and a process for preparation thereof.