A synchrotron radiation study of the one‐dimensional complex of sodium with (1S)‐N‐carboxylato‐1‐(9‐deazaadenin‐9‐yl)‐1,4‐dideoxy‐1,4‐imino‐d‐ribitol,a member of the 'immucillin' family

The sodium salt of [immucillin‐A–CO₂H]⁻ (Imm‐A), namely catena‐poly[[[triaquadisodium(I)](μ‐aqua)[μ‐(1S)‐N‐carboxylato‐1‐(9‐deazaadenin‐9‐yl)‐1,4‐dideoxy‐1,4‐imino‐d ‐ribitol][triaquadisodium(I)][μ‐(1S)‐N‐carboxylato‐1‐(9‐deazaadenin‐9‐yl)‐1,4‐dideoxy‐1,4‐imino‐d ‐ribitol]] tetrahydrate], {[Na₂(C₁₂H₁₃N₄O₆)₂(H₂O)₇]·4H₂O}_n, (I), forms a polymeric chain via Na⁺—O interactions involving the carboxylate and keto O atoms of two independent Imm‐A molecules. Extensive N,O—H...O hydrogen bonding utilizing all water H atoms, including four waters of crystallization, provides crystal packing. The structural definition of this novel compound was made possible through the use of synchrotron radiation utilizing a minute fragment (volume ∼2.4 × 10⁻⁵ mm⁻³) on a beamline optimized for protein data collection. A summary of intra‐ring conformations for immucillin structures indicates considerable flexibility while retaining similar intra‐ring orientations.     

Synthesen und Strukturen von Bis(4,4′‐t‐butyl‐2,2′‐bipyridin)‐Ruthenium(II)‐Komplexen mit funktionellen Derivaten des Tetramethyl‐bibenzimidazols

Syntheses and Structures of Bis(4,4′‐t‐butyl‐2,2′‐bipyridine) Ruthenium(II) Complexes with functional Derivatives of Tetramethyl‐bibenzimidazole [(tbbpy)₂RuCl₂] reacts with dinitro‐tetramethylbibenzimidazole ( A ) in DMF to form the complex [(tbbpy)₂Ru( A )](PF₆)₂ ( 1a ) (tbbpy: bis(4,4′‐t‐butyl)‐2,2′bipyridine). Exchange of the two PF₆^? anions by a mixture of tetrafluor‐terephthalat/tetrafluor‐terephthalic acid results in the formation of 1b in which an extended hydrogen‐bonded network is formed. According to the ¹H NMR spectra and X‐ray analyses of both 1a and 1b , the two nitro groups of the bibenzimidazole ligand are situated at the periphery of the complex in cis position to each other. Reduction of the nitro groups in 1a with SnCl₂/HCl results in the corresponding diamino complex 2 which is a useful starting product for further functionalization reactions. Substitution of the two amino groups in 2 by bromide or iodide via Sandmeyer reaction results in the crystalline complexes [(tbbpy)₂Ru( C )](PF₆)₂ and [(tbbpy)₂Ru( D )](PF₆)₂ ( C : dibromo‐tetrabibenzimidazole, D : diiodo‐tetrabibenzimidazole). Furthermore, 2 readily reacts with 4‐t‐butyl‐salicylaldehyde or pyridine‐2‐carbaldehyde under formation of the corresponding Schiff base Ru^II complexes 5 and 6 . ¹H NMR spectra show that the substituents (NH₂, Br, I, azomethines) in 2 ‐ 6 are also situated in peripheral positions, cis to each other. The solid state structure of both 2 , and 3 , determined by X‐ray analyses confirm this structure. In addition, the X‐ray diffraction analyses of single crystals of the complexes [(tri‐t‐butyl‐terpy)(Cl)Ru( A )] ( 7 ) and [( A )PtCl₂] ( 8 ) display also that the nitro groups in these complexes are in a cis‐arrangement.     

Channel‐forming solvate crystals and isostructural solvent‐free powder of 5‐hydroxy‐6‐methyl‐2‐pyridone

Crystals of 5‐hydroxy‐6‐methyl‐2‐pyridone, (I), grown from a variety of solvents, are invariably trigonal (space group R); these are 5‐hydroxy‐6‐methyl‐2‐pyridone acetone 0.1667‐solvate, C₆H₇NO₂·0.1667C₃H₆O, (Ia), and 6‐methyl‐5‐hydroxy‐2‐pyridone propan‐2‐ol 0.1667‐solvate, C₆H₇NO₂·0.1667C₃H₈O, (Ib), and the forms from methanol, (Ic), water, (Id), benzonitrile, (Ie), and benzyl alcohol, (If). They incorporate channels running the length of the c axis that contain extensively disordered solvent molecules. A solvent‐free sublimed powder of 5‐hydroxy‐6‐methyl‐2‐pyridone microcrystals is essentially isostructural. Inversion‐related host molecules interact via pairs of N—H...O hydrogen bonds to form R₂²(8) dimers. Six of these dimers form large R₁₂⁶(42) puckered rings, in which the O atom of each N—H...O hydrogen bond is also the acceptor in an O—H...O hydrogen bond that involves the 5‐hydroxy group. The large R₁₂⁶(42) rings straddle the axes and form stacked columns viaπ–π interactions between inversion‐related molecules of (I) [mean interplanar spacing = 3.254 Å and ring centroid–centroid distance = 3.688 (2) Å]. The channels are lined by methyl groups, which all point inwards to the centre of the channels.     

Supramolecular aggregation in three 4‐aryl‐6‐(1H‐indol‐3‐yl)‐3‐methyl‐1‐phenyl‐1H‐pyrazolo[3,4‐b]pyridine‐5‐carbonitriles

Both 6‐(1H‐indol‐3‐yl)‐3‐methyl‐4‐(4‐methylphenyl)‐1‐phenyl‐1H‐pyrazolo[3,4‐b]pyridine‐5‐carbonitrile and 6‐(1H‐indol‐3‐yl)‐3‐methyl‐4‐(4‐methoxyphenyl)‐1‐phenyl‐1H‐pyrazolo[3,4‐b]pyridine‐5‐carbonitrile crystallize from dimethylformamide solutions as stoichiometric 1:1 solvates, viz. C₂₉H₂₁N₅·C₃H₇NO, (I), and C₂₉H₂₁N₅O·C₃H₇NO, (II), respectively; however, 6‐(1H‐indol‐3‐yl)‐3‐methyl‐1‐phenyl‐4‐(3,4,5‐trimethoxyphenyl)‐1H‐pyrazolo[3,4‐b]pyridine‐5‐carbonitrile, C₃₁H₂₅N₅O₃, (III), crystallizes in the unsolvated form. The heterocyclic components of (I) are linked by C—H...π(arene) hydrogen bonds to form cyclic centrosymmetric dimers, from which the solvent molecules are pendent, linked by N—H...O hydrogen bonds. In (II), the heterocyclic components are linked by a combination of C—H...N and C—H...π(arene) hydrogen bonds into chains containing two types of centrosymmetric ring, and the pendent solvent molecules are linked to these chains by N—H...O hydrogen bonds. Molecules of (III) are linked into simple C(12) chains by an N—H...O hydrogen bond, and these chains are weakly linked into pairs by an aromatic π–π stacking interaction.     

Synthesis of three‐armed poly(trans‐4‐hydroxy‐N‐benzyloxycarbonyl‐L‐proline)‐block‐poly(ε‐caprolactone) copolymers

A series of novel types of three‐armed poly(trans‐4‐hydroxy‐N‐benzyloxycarbonyl‐L ‐proline)‐block‐poly(ε‐caprolactone) (PHpr‐b‐PCL) copolymers were successfully synthesized via melt block copolymerization of trans‐4‐hydroxy‐N‐benzyloxycarbonyl‐L ‐proline (N‐CBz‐Hpr) and ε‐caprolactone (ε‐CL) with a trifunctional initiator trimethylolpropane (TMP) and stannous octoate (SnOct₂) as a catalyst. For the homopolycondensation of N‐CBz‐Hpr with TMP initiator and SnOct₂ catalyst, the number‐average molecular weight (M_n) of prepolymer increases from 530 to 3540 g mol^?1 with the molar ratio of monomer to initiator (3–30), and the molecular weight distribution (M_w/M_n) is between 1.25 to 1.32. These three‐armed prepolymer PHpr were subsequently block copolymerized with ε‐caprolactone (ε‐CL) in the presence of SnOct₂ as a catalyst. The M_n of the copolymer increased from 2240 to 18,840 g mol^?1 with the molar ratio (0–60) of ε‐CL to PHpr. These products were characterized by differential scanning calorimetry (DSC), ¹H NMR, and gel permeation chromatography. According to DSC, the glass‐transition temperature (T_g) of the three‐armed polymers depended on the molar ratio of monomer/initiator that were added. In vitro degradation of these copolymers was evaluated from weight‐loss measurements and the change of M_n and M_w/M_n. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1708–1717, 2005     

Hydrogen‐bonding patterns in three substituted N‐benzyl‐N‐(3‐tert‐butyl‐1‐phenyl‐1H‐pyrazol‐5‐yl)acetamides

The molecules of N‐(3‐tert‐butyl‐1‐phenyl‐1H‐pyrazol‐5‐yl)‐2‐chloro‐N‐(4‐methoxybenzyl)acetamide, C₂₃H₂₆ClN₃O₂, are linked into a chain of edge‐fused centrosymmetric rings by a combination of one C—H...O hydrogen bond and one C—H...π(arene) hydrogen bond. In N‐(3‐tert‐butyl‐1‐phenyl‐1H‐pyrazol‐5‐yl)‐2‐chloro‐N‐(4‐chlorobenzyl)acetamide, C₂₂H₂₃Cl₂N₃O, a combination of one C—H...O hydrogen bond and two C—H...π(arene) hydrogen bonds, which utilize different aryl rings as the acceptors, link the molecules into sheets. The molecules of S‐[N‐(3‐tert‐butyl‐1‐phenyl‐1H‐pyrazol‐5‐yl)‐N‐(4‐methylbenzyl)carbamoyl]methyl O‐ethyl carbonodithioate, C₂₆H₃₁N₃O₂S₂, are also linked into sheets, now by a combination of two C—H...O hydrogen bonds, both of which utilize the amide O atom as the acceptor, and two C—H...π(arene) hydrogen bonds, which utilize different aryl groups as the acceptors.     

Hierarchical Structure‐Within‐Structure Morphologies in A2‐star‐(B‐alt‐C) Molecules

We employ dissipative particle dynamics (DPD) to examine the self‐assembly behavior of A₂‐star‐(B‐alt‐C) molecules. We successfully observe various types of hierarchical structure‐within‐structures, such as A‐formed spheres in the matrix formed by B and C alternating layers, hexagonally packed A‐formed cylinders in the matrix with B and C segregated layers, B and C alternating layers‐within‐lamellae, coaxial B and C alternating domains within hexagonally packed BC‐formed cylinders in the A‐matrix, and co‐centric BC‐alternating domains within BC‐formed spheres in the A‐matrix, by increasing the A composition. Generally speaking, the small length‐scale B and C segregated domains are in parallel to the large length‐scale structures. This hierarchical periodicity along the same axis as well as the various characteristic structures, that the A₂‐star‐(B‐alt‐C) copolymers display, are quite different from those in A‐block‐(B‐graft‐C) coil‐comb copolymers. Moreover, it is interesting to find that when the copolymer chain length increases, though the hierarchical structure type is maintained, the number of small length‐scale lamellae that can form within the large length‐scale structure increases. These hierarchical structures under various compositions are reported theoretically for the first time in the copolymer systems consisting of the alternating blocks, and are in good agreement with the most recent experimental work by Matsushita and co‐workers (Macromolecules 2007 , 40, 4023).     

Luminescent properties of three structures built from 3‐cyano‐4‐dicyanomethylene‐5‐oxo‐4,5‐dihydro‐1H‐pyrrol‐2‐olate and cadmium

Yellow–orange tetraaquabis(3‐cyano‐4‐dicyanomethylene‐5‐oxo‐4,5‐dihydro‐1H‐pyrrol‐2‐olato‐κN³)cadmium(II) dihydrate, [Cd(C₈HN₄O₂)₂(H₂O)₄]·2H₂O, (I), and yellow tetraaquabis(3‐cyano‐4‐dicyanomethylene‐5‐oxo‐4,5‐dihydro‐1H‐pyrrol‐2‐olato‐κN³)cadmium(II) 1,4‐dioxane solvate, [Cd(C₈HN₄O₂)₂(H₂O)₄]·C₄H₈O₂, (II), contain centrosymmetric mononuclear Cd²⁺ coordination complex molecules in different conformations. Dark‐red poly[[decaaquabis(μ₂‐3‐cyano‐4‐dicyanomethylene‐5‐oxo‐4,5‐dihydro‐1H‐pyrrol‐2‐olato‐κ²N:N′)bis(μ₂‐3‐cyano‐4‐dicyanomethylene‐1H‐pyrrole‐2,5‐diolato‐κ²N:N′)tricadmium] hemihydrate], [Cd₃(C₈HN₄O₂)₂(C₈N₄O₂)₂(H₂O)₁₀]·0.5H₂O, (III), has a polymeric two‐dimensional structure, the building block of which includes two cadmium cations (one of them located on an inversion centre), and both singly and doubly charged anions. The cathodoluminescence spectra of the crystals are different and cover the wavelength range from UV to red, with emission peaks at 377 and 620 nm for (III), and at 583 and 580 nm for (I) and (II), respectively.     

(Z)‐3‐(1H‐Indol‐3‐yl)‐2‐(3‐thienyl)­acrylo­nitrile and (Z)‐3‐[1‐(4‐tert‐butyl­benzyl)‐1H‐indol‐3‐yl]‐2‐(3‐thienyl)­acrylo­nitrile

(Z)‐3‐(1H‐Indol‐3‐yl)‐2‐(3‐thienyl)­acrylo­nitrile, C₁₅H₁₀N₂S, (I), and (Z)‐3‐[1‐(4‐tert‐butyl­benzyl)‐1H‐indol‐3‐yl]‐2‐(3‐thienyl)­acrylo­nitrile, C₂₆H₂₄N₂S, (II), were prepared by base‐catalyzed reactions of the corresponding indole‐3‐carbox­aldehyde with thio­phene‐3‐aceto­nitrile. ¹H/¹³C NMR spectral data and X‐ray crystal structures of compounds (I) and (II) are presented. The olefinic bond connecting the indole and thio­phene moieties has Z geometry in both cases, and the mol­ecules crystallize in space groups P2₁/c and C2/c for (I) and (II), respectively. Slight thienyl ring‐flip disorder (ca 5.6%) was observed and modeled for (I).     

Two 17‐hydroxy‐9(10→5)‐abeo‐estr‐4‐ene‐3,10‐diones

(5S,9S,17S)‐17‐Hydroxy‐9(10→5)‐abeo‐estr‐4‐ene‐3,10‐dione, C₁₈H₂₆O₃, (II), and (5R,9R,17S)‐17‐hydroxy‐9(10→5)‐abeo‐estr‐4‐ene‐3,10‐dione, C₁₈H₂₆O₃, (III), are equimolecular products of the Fe^II‐induced transposition of 10β‐hydro­peroxy‐17β‐hydroxyestr‐4‐en‐3‐one, (I). With respect to reagent mol­ecules, the configuration at C9 is retained for (II) while it is inverted in (III). The conformations of the five‐ and six‐membered rings are compared.     

A low‐temperature modification of hexa‐tert‐butyldisilane and a new polymorph of 1,1,2,2‐tetra‐tert‐butyl‐1,2‐diphenyldisilane

Crystals of hexa‐tert‐butyldisilane, C₂₄H₅₄Si₂, undergo a reversible phase transition at 179 (2) K. The space group changes from Ibca (high temperature) to Pbca (low temperature), but the lattice constants a, b and c do not change significantly during the phase transition. The crystallographic twofold axis of the molecule in the high‐temperature phase is replaced by a noncrystallographic twofold axis in the low‐temperature phase. The angle between the two axes is 2.36 (4)°. The centre of the molecule undergoes a translation of 0.123 (1) Å during the phase transition, but the conformation angles of the molecule remain unchanged. Between the two tri‐tert‐butylsilyl subunits there are six short repulsive intramolecular C—H...H—C contacts, with H...H distances between 2.02 and 2.04 Å, resulting in a significant lengthening of the Si—Si and Si—C bonds. The Si—Si bond length is 2.6863 (5) Å and the Si—C bond lengths are between 1.9860 (14) and 1.9933 (14) Å. Torsion angles about the Si—Si and Si—C bonds deviate by approximately 15° from the values expected for staggered conformations due to intramolecular steric H...H repulsions. A new polymorph is reported for the crystal structure of 1,1,2,2‐tetra‐tert‐butyl‐1,2‐diphenyldisilane, C₂₈H₄₆Si₂. It has two independent molecules with rather similar conformations. The Si—Si bond lengths are 2.4869 (8) and 2.4944 (8) Å. The C—Si—Si—C torsion angles deviate by between −3.4 (1) and −18.5 (1)° from the values expected for a staggered conformation. These deviations result from steric interactions. Four Si—C(t‐Bu) bonds are almost staggered, while the other four Si—C(t‐Bu) bonds are intermediate between a staggered and an eclipsed conformation. The latter Si—C(t‐Bu) bonds are about 0.019 (2) Å longer than the staggered Si—C(t‐Bu) bonds.     

1‐Ferrocenylmethyl‐3‐(2,4,6‐trimethylbenzyl)‐1H‐imidazolidin‐3‐ium iodide and trans‐bis(3‐benzyl‐1‐ferrocenylmethyl‐1H‐imidazolidin‐2‐ylidene)diiodidopalladium(II)

Owing to increasing interest in the use of N‐heterocyclic carbenes (NHCs) based on imidazolidinium ions as ligands in the design of highly efficient transition‐metal‐based homogeneous catalysts, the characterizations of the 1‐ferrocenylmethyl‐3‐(2,4,6‐trimethylbenzyl)imidazolidin‐3‐ium iodide salt, [Fe(C₅H₅)(C₁₉H₂₄N₂)]I, (I), and the palladium complex trans‐bis(3‐benzyl‐1‐ferrocenylmethyl‐1H‐imidazolidin‐2‐ylidene)diiodidopalladium(II), [Fe₂Pd(C₅H₅)₂(C₁₆H₁₇N₂)₂I₂], (II), are reported. Compound (I) has two iodide anions and two imidazolidinium cations within the asymmetric unit (Z′ = 2). The two cations have distinctly different conformations, with the ferrocene groups orientated exo and endo with respect to the N‐heterocyclic carbene. Weak C—H donor hydrogen bonds to both the iodide anions and the π system of the mesitylene group combine to form two‐dimensional layers perpendicular to the crystallographic c direction. Only one of the formally charged imidazolidinium rings forms a near‐linear hydrogen bond with an iodide anion. Complex (II) shows square‐planar coordination around the Pd^II metal, which is located on an inversion centre (Z′ = 0.5). The ferrocene and benzyl substituents are in a trans–anti arrangement. The Pd—C bond distance between the N‐heterocyclic carbene ligands and the metal atom is 2.036 (7) Å. A survey of related structures shows that the lengthening of the N—C bonds and the closure of the N—C—N angle seen here on metal complexation is typical of similar NHCs and their complexes.     

4‐Ethynyl‐4‐hydroxycyclohexan‐1‐one and 4‐ethynyl‐4‐hydroxy‐2,3,5,6‐tetramethylcyclohexa‐2,5‐dien‐1‐one

The title compounds, C₈H₁₀O₂, (I), and C₁₂H₁₄O₂, (II), occurred as by‐products in the controlled synthesis of a series of bis­(gem‐alkynols), prepared as part of an extensive study of synthon formation in simple gem‐alkynol derivatives. The two 4‐(gem‐alkynol)‐1‐ones crystallize in space group P2₁/c, (I) with Z′ = 1 and (II) with Z′ = 2. Both structures are dominated by O—H?O=C hydrogen bonds, which form simple chains in the cyclo­hexane derivative, (I), and centrosymmetric dimers, of both symmetry‐independent mol­ecules, in the cyclo­hexa‐2,5‐diene, (II). These strong synthons are further stabilized by C[triple‐bond]C—H?O=C, C_methylene—H?O(H) and C_methyl—H?O(H) interactions. The direct intermolecular interactions between donors and acceptors in the gem‐alkynol group, which characterize the bis­(gem‐alkynol) analogues of (I) and (II), are not present in the ketone derivatives studied here.     

Cationic ring‐opening polymerization of 1,6‐anhydro‐2,3,4‐tri‐O‐allyl‐β‐D‐glucopyranose as a convenient synthesis of dextran

For the convenient synthesis of (1→6)‐α‐D ‐glucopyranan, i. e., dextran ( 4 ), ring‐opening polymerization of 1,6‐anhydro‐2,3,4‐tri‐O‐allyl‐β‐D ‐glucopyranose ( 1 ) has been carried out using BF₃·OEt₂. With a ratio of [BF₃·OEt₂]/[ 1 ] = 0.5 at 0 °C for 140 h, the yield and M_n of the obtained polymer are 84.0% and 21 700, respectively. The polymer consists of (1→6)‐α‐linked 2,3,4‐tri‐O‐allyl‐D ‐glucopyranose ( 2 ) which is similar to the results for the cationic ring‐opening polymerization of 1,6‐anhydro‐2,3,4‐tri‐O‐methyl‐β‐D ‐glucopyranose and 1,6‐anhydro‐2,3,4‐tri‐O‐ethyl‐β‐D ‐glucopyranose. Polymer 2 was isomerized using tris(triphenylphosphine)‐chlororhodium as the catalyst in toluene/ethanol/water to yield polymeric 2,3,4‐tri‐O‐propenyl‐(1→6)‐α‐D ‐glucopyranan ( 3 ). Deprotection of the propenyl ether linkage of 3 was then performed using hydrochloric acid in acetone to give 4 .     

Five N′‐benzylidene‐N‐methylpyrazine‐2‐carbohydrazides

The compounds N′‐benzylidene‐N‐methylpyrazine‐2‐carbohydrazide, C₁₃H₁₂N₄O, (IIa), N′‐(2‐methoxybenzylidene)‐N‐methylpyrazine‐2‐carbohydrazide, C₁₄H₁₄N₄O₂, (IIb), N′‐(4‐cyanobenzylidene)‐N‐methylpyrazine‐2‐carbohydrazide dihydrate, C₁₄H₁₁N₅O·2H₂O, (IIc), N‐methyl‐N′‐(2‐nitrobenzylidene)pyrazine‐2‐carbohydrazide, C₁₃H₁₁N₅O₃, (IId), and N‐methyl‐N′‐(4‐nitrobenzylidene)pyrazine‐2‐carbohydrazide, C₁₃H₁₁N₅O₃, (IIe), have dihedral angles between the pyrazine rings and the benzene rings in the range 55–78°. These methylated pyrazine‐2‐carbohydrazides have supramolecular structures which are formed by weak C—H...O/N hydrogen bonds, with the exception of (IIc) which is hydrated. There are π–π stacking interactions in all five compounds. Three of these structures are compared with their nonmethylated counterparts, which have dihedral angles between the pyrazine rings and the benzene rings in the range 0–6°.     

Synthesis and Characterization of New 3‐(3‐Hydroxyphenyl)‐4‐ alkyl‐3,4‐dihydrobenzo[e][1,3]oxazepine‐1,5‐dione Compounds

A series of 3‐(3‐hydroxyphenyl)‐4‐alkyl‐3,4‐dihydrobenzo[e][1,3]oxazepine‐1,5‐dione compounds with general formula C_nH_2n+1CNO(CO)₂C₆H₄(C₆H₄OH) in which n are even parity numbers from 2 to 18. The structure determinations on these compounds were performed by FT‐IR spectroscopy which indicated that the terminal alkyl chain attached to the oxazepine ring was fully extended. Conformational analysis in DMSO at ambient temperature was carried out for the first time via high resolution ¹H NMR and ¹³C NMR spectroscopy.     

Hydrogen‐bonded chains of rings in 1‐(4‐chloroanilinomethyl)‐5‐(4‐chlorophenyl)‐1,3,5‐triazinane‐2‐thione and hydrogen‐bonded sheets in 1‐anilinomethyl‐5‐phenyl‐1,3,5‐triazinane‐2‐thione

In 1‐(4‐chloroanilinomethyl)‐5‐(4‐chlorophenyl)‐1,3,5‐triazinane‐2‐thione, C₁₆H₁₆Cl₂N₄S, there are two independent molecules in the asymmetric unit which form inversion dimers via two weak N—H...S hydrogen bonds. The dimers are then linked into C(9)C(14) chains by a C—H...S hydrogen bond and a C—H...Cl contact. In 1‐(anilinomethyl)‐5‐phenyl‐1,3,5‐triazinane‐2‐thione, C₁₆H₁₈N₄S, molecules are linked into complex sheets via a combination of N—H...S and C—H...π hydrogen bonds.     

5‐Hydroxyalkyl derivatives of tert‐butyl 2‐oxo‐2,5‐dihydro‐1H‐pyrrole‐1‐carboxylate: diastereoselectivity of the Mukaiyama crossed‐aldol‐type reaction

The title compounds, rac‐(1′R,2R)‐tert‐butyl 2‐(1′‐hydroxyethyl)‐3‐(2‐nitrophenyl)‐5‐oxo‐2,5‐dihydro‐1H‐pyrrole‐1‐carboxylate, C₁₇H₂₀N₂O₆, (I), rac‐(1′S,2R)‐tert‐butyl 2‐[1′‐hydroxy‐3′‐(methoxycarbonyl)propyl]‐3‐(2‐nitrophenyl)‐5‐oxo‐2,5‐dihydro‐1H‐pyrrole‐1‐carboxylate, C₂₀H₂₄N₂O₈, (II), and rac‐(1′S,2R)‐tert‐butyl 2‐(4′‐bromo‐1′‐hydroxybutyl)‐5‐oxo‐2,5‐dihydro‐1H‐pyrrole‐1‐carboxylate, C₁₃H₂₀BrNO₄, (III), are 5‐hydroxyalkyl derivatives of tert‐butyl 2‐oxo‐2,5‐dihydropyrrole‐1‐carboxylate. In all three compounds, the tert‐butoxycarbonyl (Boc) unit is orientated in the same manner with respect to the mean plane through the 2‐oxo‐2,5‐dihydro‐1H‐pyrrole ring. The hydroxyl substituent at one of the newly created chiral centres, which have relative R,R stereochemistry, is trans with respect to the oxo group of the pyrrole ring in (I), synthesized using acetaldehyde. When a larger aldehyde was used, as in compounds (II) and (III), the hydroxyl substituent was found to be cis with respect to the oxo group of the pyrrole ring. Here, the relative stereochemistry of the newly created chiral centres is R,S. In compound (I), O—H...O hydrogen bonding leads to an interesting hexagonal arrangement of symmetry‐related molecules. In (II) and (III), the hydroxyl groups are involved in bifurcated O—H...O hydrogen bonds, and centrosymmetric hydrogen‐bonded dimers are formed. The Mukaiyama crossed‐aldol‐type reaction was successful when using the 2‐nitrophenyl‐substituted hydroxypyrrole, or the unsubstituted hydroxypyrrole, and boron trifluoride diethyl ether as catalyst. The synthetic procedure leads to a syn configuration of the two newly created chiral centres in all three compounds.     

Three sterically hindered 6‐amino‐5‐cyano‐2‐methyl‐4‐(1‐naphthyl)‐4H‐pyran‐3‐carboxylate derivatives

In the title compounds, 2‐methoxyethyl 6‐amino‐5‐cyano‐2‐methyl‐4‐(1‐naphthyl)‐4H‐pyran‐3‐carboxylate, C₂₁H₂₀N₂O₄, (II), isopropyl 6‐amino‐5‐cyano‐2‐methyl‐4‐(1‐naphthyl)‐4H‐pyran‐3‐carboxylate, C₂₁H₂₀N₂O₃, (III), and ethyl 6‐amino‐5‐cyano‐2‐methyl‐4‐(1‐naphthyl)‐4H‐pyran‐3‐carboxylate, C₂₀H₁₈N₂O₃, (IV), the heterocyclic pyran ring adopts a flattened boat conformation. In (II) and (III), the carbonyl group and a double bond of the heterocyclic ring are mutually anti, but in (IV) they are mutually syn. The ester O atoms in (II) and (III) and the carbonyl O atom in (IV) participate in intramolecular C—H...O contacts to form six‐membered rings. The dihedral angles between the naphthalene substituent and the closest four atoms of the heterocyclic ring are 73.3 (1), 71.0 (1) and 74.3 (1)° for (II)–(IV), respectively. In all three structures, only one H atom of the NH₂ group takes part in N—H...O [in (II) and (III)] or N—H...N [in (IV)] intermolecular hydrogen bonds, and chains [in (II) and (III)] or dimers [in (IV)] are formed. In (II), weak intermolecular C—H...O and C—H...N hydrogen bonds, and in (III) intermolecular C—H...O hydrogen bonds link the chains into ladders along the a axis.     

Seven 5‐benzylamino‐3‐tert‐butyl‐1‐phenyl‐1H‐pyrazoles: unexpected isomorphisms,and hydrogen‐bonded supramolecular structures in zero,one and two dimensions

5‐Benzylamino‐3‐tert‐butyl‐1‐phenyl‐1H‐pyrazole, C₂₀H₂₃N₃, (I), and its 5‐[4‐(trifluoromethyl)benzyl]‐, C₂₁H₂₂F₃N₃, (III), and 5‐(4‐bromobenzyl)‐, C₂₀H₂₂BrN₃, (V), analogues, are isomorphous in the space group C2/c, but not strictly isostructural; molecules of (I) form hydrogen‐bonded chains, while those of (III) and (V) form hydrogen‐bonded sheets, albeit with slightly different architectures. Molecules of 3‐tert‐butyl‐5‐(4‐methylbenzylamino)‐1‐phenyl‐1H‐pyrazole, C₂₁H₂₅N₃, (II), are linked into hydrogen‐bonded dimers by a combination of N—H...π(arene) and C—H...π(arene) hydrogen bonds, while those of 3‐tert‐butyl‐5‐(4‐chlorobenzylamino)‐1‐phenyl‐1H‐pyrazole, C₂₀H₂₂ClN₃, (IV), form hydrogen‐bonded chains of rings which are themselves linked into sheets by an aromatic π–π stacking interaction. Simple hydrogen‐bonded chains built from a single N—H...O hydrogen bond are formed in 3‐tert‐butyl‐5‐(4‐nitrobenzylamino)‐1‐phenyl‐1H‐pyrazole, C₂₀H₂₂N₄O₂, (VI), while in 3‐tert‐butyl‐5‐(3,4,5‐trimethoxybenzylamino)‐1‐phenyl‐1H‐pyrazole, C₂₃H₂₉N₃O₃, (VII), which crystallizes with Z′ = 2 in the space group P, pairs of molecules are linked into two independent centrosymmetric dimers, one generated by a three‐centre N—H...(O)₂ hydrogen bond and the other by a two‐centre N—H...O hydrogen bond.