It's an alkylation technically and the answer depends on a lot of variables. Are you liberating ammonia gas from a compound? Are you trying to alkkylate a cyclic ring? N alkylate acarbon chain? Alpha alkalate an amine? Is it a Suzuki coupling, Friedel-crafts, menshutkin reaction, hydroamination, free-radical....? Thiol-ene, Williamson ether synth, cross coupling?