Catalysis of SnAr Reactions by Nucleophilic Molecules in Aprotic Nonpolar Media. Evidence of the Closed Structure of Associates of Primary and Secondary Amines and the Unavailability of Their Reactivity

Abstract

Ðàññìîòðåíû èçâåñòíûå ìåõàíèçìû êàòàëèçà íóêëåîôèëîì ðåàêöèé S N Ar â íåïîëÿðíûõ ñðåäàõ. Ïðåäëîaeåíû àëüòåðíàòèâíûå ñõåìû ìåõàíèçìîâ êàòàëèçà âòîðè÷íûìè è ïåðâè÷íûìè àìèíàìè, ðàâíîâåðîÿòíî ó÷èòûâàþùèå âîçìîaeíûå ïóòè ïðîöåññà. Ïðîâåäåí àíàëèç êèíåòè-÷åñêèõ ñõåì ïðè ðàçëè÷íûõ ëèìèòèðóþùèõ ñòàäèÿõ ïðîöåññà. Ïîêàçàíî, ÷òî â ñëó÷àå íàèáîëåå ìåäëåííîé ñòàäèè îáðàçîâàíèÿ σ-êîìïëåêñà êàòàëèç äîëaeåí îñóùåñòâëÿòüñÿ òîëüêî ïî àññîöèàòèâíîìó ìåõàíèçìó, à â ñëó÷àå ëèìèòèðóþùåãî ðàñïàäà-òîëüêî ïî ñòàäèéíîìó. Íàëè÷èå êàòàëèçà íóêëåîôèëîì ÿâëÿåòñÿ êðèòåðèåì ìåäëåííîé ñòàäèè ðàñïàäà ïðîìåaeóòî÷íîãî ïðîäóêòà. Ýòî ñâèäåòåëüñòâóåò îá îòñóòñòâèè ðåàêöèîííîé ñïîñîáíîñòè ñàìîàññîöèàòîâ íóêëåîôèëîâ ïåðâè÷íûõ è âòîðè÷íûõ àìèíîâ. Ïðè÷èíà òàêîãî ÿâëåíèÿ ìîaeåò áûòü â öèêëè÷åñêîì ñòðîåíèå àññîöèàòîâ. Êëþ÷åâûå ñëîâà: êàòàëèç íóêëåîôèëîì; íóêëåîôèëüíîå àðîìàòè÷åñêîå çàìåùåíèå; ïåðâè÷íûå è âòîðè÷íûå àìèíû; ïðîòîèíåðòíûå ñðåäû. Äàòà ïîñòóïëåíèÿ 25.06.18 The known mechanisms of nucleophilic catalysis of S N Ar reactions in nonpolar media are studied. Alternative schemes mechanisms of catalysis by secondary and primary amines are proposed , which are equally likely to take into account the possible ways of the process. The analysis of kinetic schemes at various limiting stages of the process are conducted. It is shown that in the case of the slowest stage of formation of σ-complex, catalysis should be carried out only by the associative mechanism, and in the case of the limiting decomposition-only by the stage. The presence catalysis of nucleophilic is a criterion for the slow decay stage of the intermediate product. This indicates the lack of reactivity of selfassociative nucleophilic primary and secondary amines. The reason for this phenomenon may be in the cyclic structure of associates.