We have discussed the grounds of modern understandings about S reactions. Quite recently??N??they used to be associated with Chichibabin reaction,hydroxylation of nitrobenzene,synthesis of??alizarin,i.e. with the processes occurring under stringent conditions,what is natural in terms of the??- high-energy nature of the displaced H particle. This situation did not stimulate chemists to investi-??gate this area. This pattern entirely changed today. Modern data on the reaction mechanism give a??clear idea of a necessity to fulfil an indirect removal of the hydride ion. This knowledge has undeni-??ably contributed much to the progress in this field of research through development of diverse and??H??convenient synthetic methods with the use of S??reactions.??N