While the Aircraft accelerates(must suppose all memory items and initial procedures completed),then i believe the PNF has time to transmit mayday and advise ATC of initial action(direction/altitude/non standard turn).
If acceleration is delayed due to airfield special initilal turn due to terrain(runway analyis Engine out special procedure),MAYDAY can be transmitted when all necessary actions are made and aircraft stable during turn).or earlier if PNF is way on top of the game and knows a few seconds spared are there to allow efficient and clear comms.
SOPS differ,know yours and think if it happens ,when would be the good time to communicate.