Versatile Cycloaddition Reactions of 1-Alkyl-1,2-Diphospholes

Abstract

The reactivity of 1-alkyl-1,2-diphospholes in cycloaddition reactions with dienes, dienophiles or 1,3-dipoles was examined. 1-Alkyl-1,2-diphospholes (2 ) exhibit dual reactivity and act as diene toward maleic acid derivatives or as dienophiles with 2,3-dimethyl-1,3-butadiene. The 1-alkenyl-1,2-diphospholes (4 ) are readily involved in intramolecular [4 + 2] cycloaddition reactions leading to cage phosphines (5 ). Interaction of 1-alkyl-1,2-diphospholes (2) with 1,3-dipolar reagents (diphenyldiazomethane and nitrones) results in formation of the bicyclic phosphiranes (8) and dimers of 1-alkyl-1,2-diphosphole oxides (9) or bicyclic phosphine oxides (10) with a β-lactam moiety depending on temperature.     

Reactions of 1-alkyl-1,2-diphospholes with 1,3-dipoles: diphenyldiazomethane and nitrones

The reaction of 1-alkyl-1,2-diphosphacyclopenta-2,4-dienes (1-alkyl-1,2-diphospholes) (1) with diphenyldiazomethane proceeds at room temperature via unstable [3+2] cycloadducts to form bicyclic phosphiranes (2). However, 1-alkyl-1,2-diphospholes (1) react with N,alpha-diphenylnitrone or N-tert-butyl-alpha-phenylnitrone depending on the temperature to give either dimers of 1-alkyl-1-oxo-1,2-diphospholes (5) or 1-alkyl-1,7-dioxo-6-azo-1,7-diphospha-bicyclo[3.2.0]hept-2-enes (7) - phosphorus analogues of β-lactams.     

Electrochemical reduction of ZnBr<Subscript>2</Subscript> in the presence of organic halides

Electrochemical reduction of zinc bromide in dimethylformamide, acetonitrile, and tetrahydrofuran in the presence of organic halides (RX) results in the formation of organozinc compounds by oxidative addition of RX to electrochemically generated Zn(0). Effects of the solvent and the nature of organic halides on the electrochemical reduction of zinc (II) ions are analyzed.     

Reactions of 1-ethyl-1,2-diphosphole with acetylenes

Russian Chemical Bulletin - The cycloaddition of 1-ethyl-3,4,5-triphenyl-1,2-diphosphacyclopenta-2,4-diene to acetylenes R1C≡CR2 (R1 = R2 = CO2Me; R1 = Ph, R2 = H) gives phosphinine along...     

NMR study of the Ni complexes based on 1-alkyl-1,2-diphospholes

Russian Chemical Bulletin - The structures of the nickel complexes based on 1-alkyl-1,2-diphospholes in a solution were determined using 1D/2D homo- and heterocorrelation NMR experiments. The...     

Electrocatalytic reduction of aryldichlorophosphines with the (2,2′-bipyridine)nickel complexes

The reduction of aryldichlorophosphines in organic solvents was studied by cyclic voltammetry, preparative electrolysis, and chemical reduction. The reaction of the electrochemically generated (2,2′-bipyridine)nickel(0) complexes with aryldichlorophosphines PhPCl₂ and tippPCl₂ (tipp is 2,4,6-triisopropylphenyl) proceeds through the formation of highly reactive organophosphorus intermediates, whose reactions with diphenylacetylene and hex-1-ene afford phosphirene and phosphirane heterocycles, respectively. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 901–907, May, 2007.