Amide-Type Substrates in the Synthesis of N-Protected 1-Aminomethylphosphonium Salts

Herein we describe the development and optimization of a two-step procedure for the synthesis of N-protected 1-aminomethylphosphonium salts from imides, amides, carbamates, or lactams. Our “step-by-step” methodology involves the transformation of amide-type substrates to the corresponding hydroxymethyl derivatives, followed by the substitution of the hydroxyl group with a phosphonium moiety. The first step of the described synthesis was conducted based on well-known protocols for hydroxymethylation with formaldehyde or paraformaldehyde. In turn, the second (substitution) stage required optimization studies. In general, reactions of amide, carbamate, and lactam derivatives occurred at a temperature of 70 °C in a relatively short time (1 h). On the other hand, N-hydroxymethylimides reacted with triarylphosphonium salts at a much higher temperature (135 °C) and over longer reaction times (as much as 30 h). However, the proposed strategy is very efficient, especially when NaBr is used as a catalyst. Moreover, a simple work-up procedure involving only crystallization afforded good to excellent yields (up to 99%).

An expedient and convenient approach for one-pot synthesis of 1H-isoindole-1,3(2H)-diones

An easy and expedient method for the one-pot synthesis of 1H-isoindole-1,3(2H)-diones has been developed by the reaction of the corresponding cyclic anhydrides with guanidinium chloride as a nitrogen source in the presence of FeCl3 as a catalyst under mild reaction conditions.

The synthesis of unsubstituted cyclic imides using hydroxylamine under microwave irradiation

Unsubstituted cyclic imides were synthesized from a series of cyclic anhydrides, hydroxylamine hydrochloride (NH₂OH∙HCl), and 4-N,N-dimethylamino-pyridine (DMAP, base catalyst) under microwave irradiation in monomode and multimode microwaves. This novel microwave synthesis produced high yields of the unsubstituted cyclic imides for both the monomode (61 - 81%) and multimode (84 - 97%) microwaves.