Direct Estirification and Amidation of Phosphinic Acids Under Microwave Conditions

Abstract

Phosphinic acids may be efficiently esterified in microwave-assisted reactions with alcohols. Especially alcohols with longer alkyl chain are suitable reagents for direct esterifications. At the same time, the direct amidation cannot be complete under such conditions. Hence, the tradional amidations via the phosphinic chloride intermediates have to be applied. The values of activation enthalpies and reaction enthalpies obtained by quantum chemical calculations justified the experimental observations. Microwave has a potential in overcoming relatively high activation enthalpies.     

Enantioselective Phase Transfer Catalytic Reactions. A Comparative Study on the Use of Cinchonidine Salts and Glucose-Based Lariat Ethers Including Phosphinoxidomethyl Derivatives

Five model reactions including an epoxidation by alkylhydroperoxide or Darzens condensation, as well as Michael additions were accomplished under phase transfer catalytic conditions using cinchonidine salts or lariat ethers with side arms having HO or Ph₂P(O) endgroups as the catalysts. In almost all cases, the use of lariat ethers with either hydroxyalkyl- or phosphinoxido N-substituents led to better enantioselectivities than that of the three cinchonidine derivatives studied.     

T3P-assisted esterification and amidation of phosphinic acids

A few phosphinic acids, such as phenylphosphinic acids, 1-hydroxy-3-phospholene 1-oxides and 1-hydroxyphospholane oxides are esterified with simple alcohols in the presence of propylphosphonic anhydride (T3P^®). If 1.1 equiv of the T3P^® reagent is used, the esterifications are fast and efficient at 25° C. In the case of more reactive models it was enough to apply 0.66 equiv of T3P^® at 85° C under microwave conditions. The amidation of 1-hydroxy-3-methyl-3-phospholene oxide could also be accomplished under similar conditions.     

T3P®-promoted Kabachnik–Fields reaction: an efficient synthesis of α-aminophosphonates

A simple and efficient synthesis of α-aminophosphonates has been developed via the one-pot three-component reactions of aldehydes, amines, and trialkyl phosphites. The reactions occurred rapidly at room temperature in the presence of 1 equiv of propylphosphonic anhydride (T3P®) as the condensing agent, and the α-aminophosphonate products were obtained in high yields.     

Microwave‐Promoted Efficient Synthesis of 2‐Phosphabicyclo[2.2.2]octadiene‐ and Octene‐2‐oxides under Solvent‐Free Conditions in Diels–Alder Reaction

The microwave‐induced and solvent‐free Diels–Alder reaction of 1,2‐dihydrophosphinine oxides (1 and 5) and dimethyl acetylenedicarboxylate or N‐phenylmaleimide afforded 2‐phosphabicyclo[2.2.2]octadiene‐ (2 and 6) and phosphabicyclo[2.2.2]octene oxides (4 and 7), respectively, almost quantitatively and in a fast reaction in an ecofriendly manner.     

The Effect of Onium Salt Additives on the Diels-Alder Reactions of a 1-Phenyl-1,2-dihydrophosphinine Oxide under Microwave Conditions

The microwave absorbing ability of toluene is increased in the presence of a slight amount (2–4 mg/3 mL) of quaternary ammonium or phosphonium salts. These additives somewhat accelerated the Diels-Alder reaction of 1-phenyl-1,2-dihydrophosphinine oxide 1 with N-phenylmaleimide and maleic acid anhydride to afford phosphabicyclo[2.2.2]octene derivatives.     

Diels–Alder Cycloadditions of 1,2-Dihydrophosphinine Oxides and Fragmentation-Related Phosphorylations with 2-Phosphabicyclo[2.2.2]Octadiene Oxides Under Green Chemical Conditions—The Role of Microwave and Ionic Liquids

Abstract

The effect of the use of microwave (MW) and solvents including ionic liquids on the Diels–Alder reaction of 1,2-dihydrophosphinine oxides (1) and fragmentation-related phosphorylation of phenols with 2-phosphabicyclo[2.2.2]octadiene oxides (4) was studied. The MW-assisted Diels–Alder reaction of dihydrophosphinine oxides (1) with N-phenylmaleimide may be advantageous to carry out in [bmim][BF₄] due to shorter reaction times, but the dimerization of the double-bond isomers (A and B) of the dihydrophosphinine oxides (1) may be best accomplished under MW in the absence of any solvent. The fragmentation-related phosphorylations may also be carried out under MW, which with the P-phenyl precursor (4a) became more efficient in [bmim][BF₄].

GRAPHICAL ABSTRACT      

Synthesis of Bis(phosphinoyl)amines and Phosphinoyl–Phosphorylamines by the N‐Phosphinoylation and N‐Phosphorylation of 1‐Alkylamino‐2,5‐dihydro‐1H‐phosphole 1‐Oxides

The N‐phosphinoylation and N‐phosphorylation reaction of 1‐alkylamino‐2,5‐dihydro‐1H‐phosphole 1‐oxides with diphenylphosphinoyl chloride and diethylphosphoryl chloride/diphenylphosphoryl chloride afforded new families of compounds comprising bis(phosphinoyl)amines and phosphinoyl‐phosphorylamines, respectively, whose stereostructures were elucidated by B3LYP/6‐31G(d,p) and B3LYP/6‐31G++(d,p) calculations. The P analogues of the mixed imides may be valuable intermediates in syntheses.     

The Formation of Phosphacycloheptatrienes in Ring Enlargement Reaction

Abstract

The forrmation of substituted phosphacycloheptatrienes in ring expansion reaction(s) is describzd. From thc: reac-tion of 3,4-dimethyl-l-phenyl-3-phospholene-l-oxide(1,R¹ = c₆H₅, R₂=R₃ = CH₃) with dichlorocarbene under liquid-liquid phase transfer circumstances not the expected adduct but the appropriate phoshacycloheptatrisne (4, R_l, R₂,R₃ as above) was prepared. The formation of this product can be explained assuming two ring expansions effected by two series of dichlorocarbene addition and cyclopropane ring opening. In the similar reaction of the methoxy-phospholenc derivative (1, R¹=CH₃O, R² = R³ = CH3 four other products are also formed beside the phosphacyclohcptatriene. Again phosphacycloheptatrienes (4) are formed as the result of dichlorocarbene addition to the regioisoners of dihidrophosphorins (2) obtained from the phospholene-dichlorocarbene adducts by thermolysis. The same product can be derived from each regioisomeric pair.