ELEMENT – PHOSPHOR – HETEROCYCLEN

Abstract

Amino-, hydroxy- and mercapto-organophosphines of the general formula may be obtained by several methods. They react with compounds possessing a carbonyl function yielding 1,3-aza-, 1,3-oxa-, 1,3-thiaphospholanes and phosphorinanes, respectively, or the corresponding compounds with the condensed benzene rings. During the formation of the E[sbnd]P-heterocycles, the existence of a carbonium-like transition state H[sbnd]P[sbnd]R[sbnd]E[dbnd]C[dbnd] is discussed as an essential intermediate produced during the cyclization. The intermediate product is favored by nitrogen, oxygen, and sulfur and by a charge exchange according to a p p-interaction. Thus, the cycloceondensation reaction corresponds to modified amino-alkylization and acetalizations, respectively, which among other things conforms to the behavior of the acylization properties of the aminoalkyl-phosphines. A reaction via a casbonium ion in the neighborhood of the tervalent phosphorus atom, °C[dbnd]P[sbnd]R[sbnd]EH, is improbable, since the election pair of the phosphorus atom possesses s-character almost exclusively and cannot overlap with the vacant p _z-orbital of the carbon atom in the carbonium ion due to symmetry reasons. This view is supported by investigations which give evidence that the reaction of disecondary phosphines possessing carbonyl functions does not yield 1,3-diphosphorinanes and 1,3-diphospholanes, respectively, by cyclization but results in disecondary P-oxides with α-hydroxyphosphines as an intermediate stage. Phosphinocarbonic acids, H[sbnd]P[sbnd]R[sbnd]COOH, are used as starting materials for the synthesis of the 1,3-aza- and 1,3-oxaphospholan-5-ones. The reactions with aldehydes and ketones, respectively, or azomethines as well as semicarbazones and hydrazones, respectively, occurs like a lactonization and a lactamization, respectively, with α-hydroxy- and α-amino-phosphines, respectively, as intermediates. The (3-oxo-alkyl)-organophosphines, which are obtainable from α,β-unsaturated ketones, primary phosphines, and alkali phosphides, may be transformed to the tetrahydro-1,3-azaphosphorines by reaction with aldehydes in the presence of ammonia or by interaction with aldimines. Besides the possibilities for the synthesis of 1,4-aza-, thia-, and oxaphosphorines, respectively, those for 2-organoelement-1,3-diphosphorinanes as well as diphospholanes are discussed. The synthesized E[sbnd]P-heterocycles show the typical reaction behavior of the other heteroatom. The structure of the compounds is supported by chemical and spectroscopic investigations. The existence of the cis-transisomer of these heterocycles has been proven on the basis of ¹H-nmr spectra.