New transformations of phosphorylthioformic acid morpholides
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Russian Chemical Bulletin, International Edition, Vol. 69, No. 8, pp. 1604—1606, August, 2020
New transformations of phosphorylthioformic acid morpholides M. A. Kozlov, Y. A. Volkova, and I. V. Zavarzin N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 119991 Moscow, Russian Federation. E-mail: [email protected] Phosphorylthioformic acid morpholides can be successfully used as a precursor in the synthesis of complexes of phosphoryl-substituted thiohydrazides with hydrazine and morpholine. The reaction of sterically hindered phosphorylthioformic acid morpholides with hydrazine hydrate proceeds chemoselectively with the formation of hydrazono(morpholino)methylphosphodiamides. Key words: phosphorylamides, thiomorpholides, thiohydrazides, phosphorylthioformic acid morpholides.
Thiocarboxylic acid morpholides are widely used in organic chemistry as precursors in the synthesis of both linear and heterocyclic structures.1 In particular, let us mention the recently developed methods for the synthesis of 1,3-thiazoles, 2 benzothiazoles, 3 N(S)-allyl thio oxamides,4 polyamides,5,6 etc. However, there are almost no literature data on the reactivity of phosphorus-containing analogs of thiocarboxylic acid morpholides, i.e., phosphorylthioformic acid morpholides. Recently,7,8 we have shown that phosphorylthioformic acid morpholides in the reactions with hydrazine can give phosphorylthioformic acid thiohydrazides. In the present work, we study the effect of the morpholide structure and conditions on the course of this reaction. The starting morpholides were synthesized according to our procedure8 from phosphinyl chlorides, morpholine, and molecular sulfur. It was found that P-(morpholin-4-ylcarbothionyl)N,N´-diphenylphosphodiamide (1) reacts with hydrazine hydrate to form complexes 2 and 3 depending on the ratio of reagents (Scheme 1). Thus, carrying out the reaction with 1.5 equiv. of hydrazine hydrate leads to the complex of thiohydrazide with one molecule of morpholine (2) in 74% yield, while the use of 3.5 equiv. of hydrazine hydrate gave complex 3 of the composition L•(N2H4)2•H2O in 78% isolated yield. Both complexes are stable and can be of interest as synthetic equivalents of free phosphorylthioformic acid thiohydrazide. The study of the reactions of sterically hindered N,N,N´,N´-tetraethyl-P-(morpholin-4-ylcarbothionyl)phosphodiamide (4) under similar conditions showed that they do not lead to the target hydrazide 5 (Scheme 2, Table 1). It was found that, regardless of the reaction conditions, the main product was N,N,N´,N´-tetraethylhydrazono(morpholino)methylphosphodiamide (6). Varying solvents, temperature conditions, reaction time, and amount
Scheme 1
Reagents and conditions: i. NH2NH2•H2O (1.5 equiv.), 1,4-dioxane, 25 C, 1 h. ii. NH2NH2•H2O (3.5 equiv.), 1,4-dioxane, 25 C, 1 h. Scheme 2
of hydrazine hydrate showed that the maximum yield of product 6 equal to 62% was achieved upon reflux with 100 equiv. of hydrazine hydrate in 1,4-dioxane; the complete conversion o
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