A Mild, Selective, PyBOP Mediated Procedure for the Conversion of Primary Amines into Phthalimides

Abstract

A new method for the protection of primary amines or amino alcohols as phthalimides is described. The phthaloyl group is selectively introduced under mild, anhydrous conditions by reacting the amine with 2-(ethoxycarbonyl)benzoic acid activated by PyBOP, followed by the thermally induced cyclization of the resulting phthalamic ester. These reaction conditions are applicable to a variety of primary amines and good yields are obtained in all cases.

Efficient Access to Alanine Derivatives by 1,4‐Additions of Potassium Trifluoro(organo)borates

“…Purification by silica gel chromatography (eluent: cyclohexane/ethyl acetate) afforded analytically pure products. Compounds 3a, [17] 3c, [18] 3f, [19] 3g, [20] 3h, [21] 3i, [22] 3j, [22] 3k, [23] 3l, [24] 3m, [25] and 3q [26] show identical physical data to that previously reported in the literature.…”

Synthesis of Nα-Tetrachlorophthaloyl (TCP)-Protected Amino Acids under Microwave Irradiation (MWI)

“…7 The phthaloyl group has also been introduced by reacting the amine with 2-(ethoxycarbonyl)benzoic acid activated by PyBOP (benzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluoro phosphate), followed by the thermally induced cyclization of the resulting phthalamic ester. 8 On the other hand, the use of microwave irradiation in organic synthesis has been extensively reported. 9 Microwave assisted reactions can be carried out safely using conventional glassware in domestic microwave ovens, resulting on savings in reaction time and waste disposal.…”

(1H-Benzotriazol-1-yloxy)tripyrrolidino-phosphonium Hexafluorophosphate

“…PyBOP also gives good results when used for the synthesis of macrolactams (eq 8), 40 (8) Formation of Amide-like linkages. PyBOP has been used (1) to activate monothiocarboxylic acids to prepare thioamides, 43 (2) to prepare the sulfonamide 'safety-catch' linker in high yield and without racemization (eq 9), 18 and (3) PyBOP has also been used as a mild, selective reagent for the conversion of primary amines to phthalimides (eq 11), 45 and to obtain excellent yields of 3,5-pyrazolidinediones (eq 12). 46 CO …”