Synthesis and crystal structure of (S)-pindolol

Racemic 3-(4-indolyloxy)-1,2-propanediol 2 has been effectively resolved into (S)- and (R)-enantiomers by a preferential crystallization procedure. Non-racemic (S)-2 was converted into (S)-4-(2,3-epoxypropoxy)-1H-indole (S)-4 via a Mitsunobu reaction and then into (S)-pindolol (S)-1. The crystalline (S)-1 was studied by single crystal X-ray diffraction. A large number of symmetry independent molecules (Z′ = 6) led to a weakening of the system of strong intermolecular hydrogen bonds, which combined with a loose packing (PI = 64.6%), may be the cause of the abnormally low melting point of (S)-1 as compared with rac-1.     

Regioselective alkylation of the lower rim of p-tert-butylthiacalix[4]arene with N-(p-nitrophenyl)-α-bromoacetamide

The preparation of partially substituted thiacalix[4]arenes 2–6 has been accomplished by conducting the reaction of the thiacalixarene 1 with N-(p-nitrophenyl)-α-bromoacetamide in acetone or acetonitrile in the presence of M₂CO₃ (M = Na, K and Cs). The influence of the reaction conditions (temperature, time, solvent, ratio of the reagents and the nature of the alkali metal carbonate) on regio- and stereoselectivity of this reaction is described.     

Reaction of arylenedioxytrihalophosphoranes with acetylenes 11. Electronic effect of the substituent in arylacetylene on the reaction rate

The reactions of 2,2,2-trichlorobenzo-1,3,2-dioxaphosphole and its benzo-substituted derivatives with arylacetylenes containing strong +M-donors and -M-acceptors afford benzo[e]-1,2-oxaphosphinine 2-oxides (phosphacoumarins) in high yields. Studies by the competitive reaction method showed that the reaction rate is sensitive to the electronic nature of the substituent in arylacetylene. Thus, the introduction of +M-donors into the phenyl ring of arylacetylene leads to an increase in the reaction rate, whereas the introduction of -M-acceptors results in its substantial decrease. The molecular and supramolecular structures of selected 2-hydroxyphosphacoumarins and substituted vinylphosphonate, which is generated by the cleavage of the P-heterocycle, were studied by X-ray diffraction.     

Crystallization of racemic 4-arylsulfonyl-2(5H)-furanones: reproducibility of homochiral associates,conditions for the spontaneous resolution of enantiomers and the formation of racemic compounds,the role of intermolecular interactions

Crystallization of three 4-arylsulfonyl-2(5H)-furanones from chloroform leads to the formation of a conglomerate of sulfone with para-tolyl substituent and racemic crystals of chloro and bromo analogs. The high degree of similarity of the crystal packings of a homochiral crystal and racemic compounds, viz., the similar type of the homochiral hydrogen-bonded chains and analogous three-dimensional homochiral layers additionally stabilized by the interactions of the type C=O…C=O and C-H…O, allowed us to suggest the presence of the second, “missing” form for each sulfone. A directed search for the “missing” forms revealed the existence of the racemic modification of sulfone with the para-tolyl fragment formed during a very slow crystallization of the compound from benzene. No conglomerates of bromo and chloro analogs were found. Topological analysis of the electron density distribution performed by quantum chemical calculations using density functional theory (PBE1PBE, 6–31G(d,p)) showed the higher energy favorability of intermolecular interactions in the homochiral chains as compared to the hypothetical heterochiral associates.     

Formation of the cage-like phosphoranes with the P-C and P-N bonds in the reactions of 2-(2-benzylidenamino)phenoxy-4-tert-butylbenzo-1,3,2-dioxaphosphol with ethyl mesoxalate and ethyl trifluoropyruvate

The reaction of 2-(2-benzylidenamino)phenoxy-4-tert-butylbenzo-1,3,2-dioxaphosphol with ethyl mesoxalate and ethyl trifluoropyruvate resulted in the formation of tricyclic phosphoranes with the P-C and P-N bonds. The adduct emerged from the initial reaction of the P^III derivative with the activated ketone (1: 1), further underwent the transformation via the intramolecular reaction involving the benzylideniminoaryl substituent, which resulted in the formation of the cage-like phosphoranes.     

Dimephosphone analogs: II. Dialkyl(diaryl)-(2-methyl-4-oxopent-2-yl)phosphine oxide oximes: Synthesis,structure, and generation of iminoxyl radicals

Dialkyl(diaryl)-(2-methyl-4-oxopent-2-yl)phosphine oxide oximes have been synthesized for the first time. According to the X-ray diffraction data, these compounds in crystal exist as a single E isomer. Their structure in solution and the E/Z isomer ratio were determined by ¹H and ¹³C NMR spectroscopy.     

Synthesis and structure of Meisenheimer adducts in nucleophilic aromatic amination of 4,6-dinitrobenzofuroxan

Stable crystalline σ-complexes (Meisenheimer adducts) were isolated for the first time in the reactions of superelectrophilic 4,6-dinitrobenzofuroxan with dodecyl- and hexadecylamines, and their structure was determined by X-ray analysis.     

An unusual reaction of cyclopropenylphosphonium bromide with sodium polyphosphides – A novel approach to sodium 3,4,5-triphenyl-1,2-diphosphacyclopentadienide

1,2,3-Triphenylcyclopropenylphosphonium bromide reacts with sodium polyphosphides to give sodium 3,4,5-triphenyl-1,2-diphosphacyclopentadienide in high yield.     

Solvent-dependent formation of two different Cd(II) complexes with p-BrC6H4C(S)NHP(O)(OiPr)2 (HL). Crystallographic modification of Cd(HL)2L2

Reaction of the potassium salt of N-(diisopropoxyphosphoryl)-p-bromothiobenzamide p-BrC₆H₄C(S)NHP(O)(OiPr)₂ (HL) with Cd(II) cations in freshly dried and distilled EtOH leads exclusively to the complex [Cd(p-BrC₆H₄C(S)NH₂-S)(L-O,S)₂] ([Cd(L^I)L₂]), while the same reaction in H₂O leads to the complex [Cd(HL-O)₂(L-O,S)₂] ([Cd(HL)₂L₂]). The corresponding reactions with Zn(II) always lead to the complex [Zn(L-O,S)₂] ([ZnL₂]) regardless of the solvent. The crystal structure of [Cd(HL)₂L₂]^.2/3H₂O reveals to be a polymorph to the previously reported anhydrous [Cd(HL)₂L₂].