Synthesis and Proton Dissociation Properties of Arylphosphonates: A Microwave‐Assisted Catalytic Arbuzov Reaction with Aryl Bromides

A series of substituted diethyl arylphosphonates was synthesized by the microwave‐assisted Arbuzov reaction of triethyl phosphite and aryl bromides in the presence of NiCl₂ as the catalyst under solvent‐free conditions in good yields. The resulting phosphonates were hydrolyzed to the corresponding arylphosphonic acids whose acidity was evaluated by physicochemical methods.     

A new family of platinum(II) complexes incorporating five‐ and six‐membered cyclic phosphine ligands

New platinum complexes of the type cis‐Pt(L)₂Cl₂ have been synthesized from five‐ and six‐membered cyclic phosphines, which were prepared after deoxygenating a series of phosphine oxides (3‐phospholene oxides, phospholane oxides, a 1,4‐dihydrophosphinine oxide, and a 1,2,3,6‐tetrahydrophosphinine oxide). The complexes were characterized by NMR and mass spectral data, and their stereostructures were elucidated by B3LYP/6‐31G(d)‐LANL2DZ ECP calculations. The phosphine intermediates were characterized as the corresponding phosphine‐boranes. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:63–70, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20579     

Synthesis of α‐aminophosphonates from α‐hydroxyphosphonates; a theoretical study

Two types of reactions, namely the Pudovik reaction of benzaldehyde and acetophenone with diethyl phosphite as well as the substitution of the α‐hydroxyphosphonates so‐formed by primary amines to afford α‐aminophosphonates, were evaluated by quantum chemical calculations at the B3LYP/6‐31G(d,p) level. An unexpected neighboring group effect was found to enhance the substitution. A series of new α‐aminophosphonates was synthesized by the microwave‐assisted substitution of α‐hydroxyphosphonates by alkylamines.     

Asymmetric cyclopropanation reactions catalyzed by carbohydrate-based crown ethers

Optically active cyclopropane derivatives were prepared by a novel, simple and green approach in high enantioselectivities using monosaccharide-based chiral crown ethers as phase transfer catalysts. The crown ethers having d-glucopyranoside, d-mannopyranoside and d-altropyranoside units proved to be efficient catalyst in a few asymmetric phase transfer cyclopropanation reactions. The Michael-initiated ring closure (MIRC) reactions of diethyl bromomalonate with chalcones took place with complete diastereoselectivity and up to 99% ee. Using benzylidenemalononitrile, 2-arylidenemalononitriles, 2-benzylidene-1,3-indandione, substituted 2-benzylidene-1,3-indandiones, 2-arylidene-1,3-indandiones and 2-benzylidene-1,3-diphenyl-1,3-propanediones enantioselectivities up to 92%, 99%, 54% 93%, 89% and 72%, respectively, were achieved, in the presence of chiral lariat ethers derived from different monosaccharides. The absolute configuration of a cyclopropane diester product was determined by a combined CD spectroscopic and theoretical study.     

Synthesis of Bis(phosphonatomethyl)-, Bis(phosphinatomethyl)-, and Bis(phosphinoxidomethyl)amines,as Well as Related Ring Bis(phosphine) Platinum Complexes

The double Kabachnik–Fields condensation of primary amines with 2 equivalents of the other reagents (formaldehyde and a >P(O)H species, such as dialkyl phosphites, diphenylphosphine oxide, as well as the related dioxaphosphorine and oxaphosphorine derivatives) carried out under microwave conditions afforded the title products in 79–94% yields. The bis(phosphinoxidomethyl)amines were converted, after double deoxygenation, to the corresponding ring platinum complexes.

Esterification of five-membered cyclic phosphinic acids under mild conditions using propylphosphonic anhydride (T3P®)

1-Hydroxy-phospholene 1-oxides (1 and 3) and 1-hydroxy-phospholane oxides (5 and 7) undergo fast and efficient esterification with a series of alcohols, at room temperature, in the presence of 1.1 equiv of propylphosphonic anhydride (T3P®).     

Microwave-Assisted Synthesis of P-Heterocycles*

Abstract

The direct esterification, thioesterification and amidation of cyclic phosphinic acids, such as 1-hydroxy-3-phospholene 1-oxides, 1-hydroxy-phospholane 1-oxides and a 1-hydroxy-1,2,3,4,5,6-hexahydrophosphinine 1-oxide, which do not take place on conventional heating, were carried out under MW conditions in excess of the alcohol, thioalcohol and amine, respectively. The cyclic phosphinates were also prepared by MW-assisted alkylating esterification of the corresponding phosphinic acids in solid–liquid phase. Using alkyl halides of normal reactivity, the application of a phase transfer catalyst was also beneficial. In addition, MW-assisted Diels–Alder reactions, so-called inverse Wittig-type reactions furnishing β-oxophosphoranes, a few kinds of phospha-Michael additions leading to precursors of bidentate P-ligands, and a few Kabachnik–Fields condensations affording α-aminophosphonates and α-aminophosphine oxides are discussed.     

Synthesis and recognition properties of α-d-glucose-based fluorescent crown ethers incorporating an acridine unit

Two new chiral glucopyranoside-based crown ethers incorporating acridine fluorescent signalling units, 15-membered ligand 1 and 21-membered ligand 2 were synthesized. Their complexation properties toward alkali and alkali earth metal ions, and their enantioselectivity towards chiral ammonium salts were studied by absorption and fluorescence spectroscopic experiments. Macrocycle 1 formed 1:1 complexes with all the metal ions selected and the stability constants were low (lg K < 2.3). The cavity-size of 2 allowed only the complexaton of organic ammonium ions. Crown 2 showed chiral discrimination in case of all the four ammonium salts used as model guest compounds; the highest enantioselectivity (K(R)/K(S) ~3) was observed for the enantiomers of phenylethyl ammonium perchlorate. Ligand 2 forms much more stable complexes with metal ions; the highest stability constant was obtained for the Ca²⁺ complex (lg K = 6.15). The coordination of metal ions by ligand 2 was accompanied by marked fluorescence enhancement, whereas the binding of ammonium ions by the same species resulted in significant fluorescence quenching.     

A Novel Reaction between the P=O Group of Cyclic 2,4,6-Trialkylphenylphosphine Oxides and Dimethyl Acetylenedicarboxylate (DMAD)

The reaction of cyclic P-aryl phosphine oxides with DMAD affords ylides/phosphoranes via oxaphosphetes.