Gyula Argay

Classification of the isostructurality of organic molecules in the crystalline state

Since its discovery by Mitscherlich in 1819, the isomorphism of crystals has been interpreted in various, sometimes controversial ways. This can be attributed to the fact that the word isomorphous refers only to the external similarities between crystalline substances. Identical or quasi-identical packing motifs of related organic substances should therefore be distinguished by a more appropriate terminology. For organic substances, in contrast with inorganic crystals, where the recommended term is isotypic, the term isostructural is unambiguous. The present work attempts to classify the main forms as isostructural and homeostructural. Within the former class, there are two subclasses distinguished by the degree of isostructurality

Stereochemical studies—76 saturated heterocycles—63 : synthesis of cis- and trans-n-methyl- and n-benzyl-4.5- and 5,6-tetramethylenetetrahydro-1,3-oxazines; an x-ray study of n-benzyl-cis-4,5-tetramethylenetetrahydro-1,-3-oxazinium- picrate

Abstract - The corresponding cis - and trans-N -methyl- and N -benzyl-5,6- and 4,5-tetramethylenetetrahydro-l,3-oxazines (5a,b-8a,b) were synthesized from cis - and trans-N -methyl and N -benzyl-2- aminomethyl-1-cyclohexanols 1a,b,2a,b , from cis - and trans-N -methyl- and N benzyl -2-hydroxymethyl-1-cyclohexylamines (3a,b,4a,b) by reaction with formaldehyde. The aminoalcohols 1a,2a,3a,b and 4a,b were prepared in considerably higher yields than in earlier procedures. NMR spectroscopy showed that the cis isomers of the synthesized oxazines were conformationally homogeneous in solution, and their preferred conformation (inside or outside) depended on the steric requirement of the groups attached to the anellation points, whereas a bulky C-2 substituent had no influence on the predominant conformation. The structure of N -benzyl- cis -4,5-tetramethylenetetrahydro-1,3-oxaziniumpicrate (7b) . determined by X-ray diffraction analysis, was in agreement with the predominant N-outside conformation of the corresponding base, established by means of NMR spectroscopy.

Crystal structures of ecdysteroids: the role of solvent molecules in hydrogen bonding and isostructurality.

Three crystal forms of the steroid 20-hydroxyecdysone were identified by single-crystal X-ray diffraction analysis: a solvent-free modification, a methanol solvate hydrate and a trihydrate. The structure of a closely related steroid, polypodine B (the 5,20-dihydroxy derivative of ecdysone), was determined in its monohydrate form. Since the unit-cell volume of unsolvated 20-hydroxyecdysone was found to be considerably smaller than that of ecdysone [Huber & Hoppe (1965). Chem. Ber. 98, 2403-2424], a new structure determination of ecdysone was performed, which confirmed the unexpected difference between the unit-cell volumes. The crystals of ecdysone and 20-hydroxyecdysone are isostructural, while the mixed solvate of 20-hydroxyecdysone is homostructural with the hydrate of polypodine B. A detailed analysis of the hydrogen-bond networks in these closely related crystal pairs highlights their packing similarities, demonstrates the role of solvent molecules, and explains the unexpectedly small cell volume of 20-hydroxyecdysone.

Saturated heterocycless—35 : Synthesis and conformational analysis of stereoisomeric 2-oxo- and 2-thioxo-cis- and trans-5,6-trimethylene-3,4,5,6-tetrahydro-1,3-oxazines

Abstract cis- and trans 5,6-Trimethylene-3,4,5,6-tetrahydro-1,3-oxazin-2-ones ane 2 thiones (11–20) were synthesized from cis and trans-2-aminomethylcyclopentanols (6–10) by reaction with urea ethyl chloroformate, carbon disulphide or thiophosgene. The cyclization reactions were also successful with the trans-amino-alcohols, at variance with earlier literature data relating to 1,2-disubstituted 1,3-bifunctional trans-cyclopentane derivatives X-Ray diffraction analysis of trans-5,6-trimethylene-3,4,5 6-tetrahydro-1,3 oxazine-2-thione (17) shows that the exocyclic CXXXS sp2 bond takes part in a co-planar delocalized pπ-pπ bond system formed on the S(10) O(1), N(3) and C(2) atoms and consequently both the C(2)-N(3) [1.304(7)a] and C(2)-O(1) [1.337(7)a] bonds gain some multiple bond character. The endocyclic bond angles at C(2) and N(3) are significantly opened, compared with those in related heterocycles. Of the bonds in the six membered hetero ring, C(5)-C(6) is significantly shortened [1.448(9)a] The remarkable ring-closure reaction of the trans cyclopentane derivatives can be explained by the above findings. 1H NMR data on compounds 11–20 suggest conformationally homogeneous systems and the predominance of the O-inside conformers of the cis isomers.

Stereochemical studies—75 : Saturated heterocycles—62. connection between the diastereoselectivity and the dominant conformation in the formation of condensed- skeleton 1,3-oxazines, first X-ray diffraction evidence of N-outside conformation

Abstract The rapid, spontaneous epimerization occurring at the C(2) chirality centre of a new diastereomeric (r-4,c-2,c-5)-2-(p-nitrophenyl)-3-methyl-4,5-tetramethylenetetrahydro-1,3-oxazine led to the conclusion that the configuration at C(2) of the bicyclic 1,3-oxazines formed by the cyclization of alicyclic 1,3-aminoalcohols with aldehydes is determined by the dominant conformation of the product. The first X-ray diffraction evidence is given for the N-outside conformation of compounds of this type.

Synthesis of vinca alkaloids and related compounds—XVI: New route to the stereoselective synthesis of (+)-vincamine, (-)-vincamone and (+)-apovincaminic acid esters

Abstract A stereoselective method has been elaborated for the synthesis of oxime esters, (-)-4a, b, from which, as common intermediates, (+)-apovincaminic acid esters (3a,b), (+)-vincamine (1) and (-)-vincamone (2) can be prepared.

Transition metal complexes with thiosemicarbazide-based ligands. Part 37.* Synthesis and study of the first Thiosemi-carbazide-derived copper(I) complexes: Crystal structure of [2-(Diphenylphosphino)benzaldehyde Thiosemicarbazonato(-1)] copper(i)-nitrate-methanol solvate

Abstract The preparation and physical characterization of two copper(I) complexes Cu(HL)NO3 and [Cu(HL)2]NO3·MeOh formed with a newly synthesized tridentate [S,N,P] HL = 2-(diphenylphosphino)benzaldehyde thiosemicarbazone ligand and the crystal structure analysis of the latter have been carried out. An X-ray study of [Cu(HL)2]NO3·MeOH revealed a copper(I) ion coordinated tetrahedrally to S,N,P,P atoms donated by two HL ligands. One is tridentate [S,N,P], whereas the second HL ligand is monodentate, ligating only its phosphorus atom to the copper. The geometry around the four-coordinate Cu(I) is comparable with Cu{N,S,P,X} tetrahedra (X = N, P, or S) retrieved from the Cambridge Structural Database. In addition, with a restriction to Cu{N,P,X,X} (X = C,N,P) tetrahedra ‐ S is excluded ‐ ca. 60 structures against

TRANSITION METAL COMPLEXES WITH THIOSEMICARBAZIDE-BASED LIGANDS. PART 28. SYNTHESIS AND X-RAY CRYSTAL STRUCTURE OF THE FIRST PHOSPHORUS-BONDED THIOSEMICARBAZIDE COMPLEX: [2-(DIPHENYLPHOSPHINO) BENZALDEHYDE THIOSEMICARBAZONATO(1-)] PYRIDINENICKEL(II)-NITRATE

Abstract The synthesis and crystal structure analysis of the diamagnetic complex [Ni(L)Py]NO3 (L = the monoanion of the newly synthesized ligand 2-(diphenylphosphino)benzaldehyde thiosemicarbazone) are reported. The complex crystallizes in the space group P21/n (No. 14) with a = 8.533(1), b = 29.123(3), c = 10.627(a) A, β = 100.36(1)°, V = 2597.8(5) A3. As revealed by X-ray analysis, the 2-(diphenylphosphino)benzaldehyde thiosemicarbazone ligand deprotonated at N(3) acts as a monoanionic tridentate donor, coordinating through SNP. The core of the bulky {Ni[(C6H5)2P-(C6H4CH=N-N=CS-NH2)·]}+ cation is a slightly puckered quadrangle formed around Ni2+ by SNP accompanied by a pyridine nitrogen. The dihedral angle of the atomic triangles S/N(4)/N(41) and P(2)/N(4)/N(41) is 18.0(4)°. The NO3 − anions are well separated from the cations which may account for the observed disorder of the oxygen atoms.

TRANSITION METAL COMPLEXES WITH THIOSEMICARBAZIDE-BASED LIGANDS. PART 25. SYNTHESIS AND X-RAY CRYSTAL STRUCTURE OF CIS-DIOXO [(SALICYLALDEHYDE THIOSEMICARBAZONATO(1-))] AQUOMOLYBDENUM (VI)CHLORIDE MONOHYDRATE, [MoO2(HL)H2O]Cl·H2O

Abstract The synthesis and crystal structure analysis of the diamagnetic complex [MoO2(HL)H2O]Cl·H2O(HL = monoanion of salicylaldehyde thiosemicarbazone) are reported. The complex crystallizes in the space group P21/a (No. 14) with a = 11.003(1), b = 8.444(1), c = 15.364(1) A, β = 104.96(1)°, V = 1379.1(2) A3. X-ray structure determination revealed that the complex possesses the usual cis-MoO2 2+ core and that the thiosemicarbazide ligand is present as a monoanionic tridentate donor coordinating through ONS. According to a search in the Cambridge Structural Database (state April 1994) this complex is the first in which the sixth coordination site at Mo(VI) is occupied by a water molecule forming a distorted octahedral coordination geometry together with the tridentate ligand.

Diaryldiacyloxyspirosulfuranes. Part 3. Sulfuranes with five-, six- and seven-membered spirorings: syntheses and molecular structures

Three novel diaryldiacyloxyspirosulfuranes (2–4) with five-, six- and seven-membered spirorings have been prepared, and their molecular structures determined by X-ray diffraction. The structure of spirosulfurane 1 with two identical five-membered spirorings has been reinvestigated. In all spirosulfuranes 1–4 the arrangement of the ligands about the central sulfur atom show a slightly distorted trigonal bipyramidal (TBP) geometry resulting in chiral molecular structure. The axial (hypervalent) S–O and equatorial (covalent) S–Car bond lengths range from 1.838(1) to 1.872(3) and from 1.771 (3) to 1.794(4)A, respectively. The axial O–S–O and equatorial Car–S–Car bond angles lie in the narrow intervals of 174.9(2)–177.4(4)° and 105.8(2)–106.9(2)°, respectively. The five-membered spirorings are practically planar in 1–3. The six-membered spirorings in 2 and 4 assume distorted sofa conformations. The seven-membered spiroring in 3, having four Car atoms with planar configuration, is irregular. The aromatic rings fused with the spirorings are perpendicular to the equatorial plane only if the spiroring is five-membered. In other cases the stable conformations with TBP geometry about sulfur involve a significant torsion of the aromatic ring about the S–Car axis. Thus, in diaryldiacyloxyspirosulfuranes having acyloxy-O ligands at axial positions the structural parameters about the sulfur are not considerably influenced by the shape and size of the spirorings. The O–S–O moiety with hypervalent bonds may be regarded as a structural unity. The sum of the individual S–O bond lengths, (3.684–3.744 A) which is characteristic of diaryldiacyloxyspirosulfuranes, differs markedly from the values found earlier for dialkoxy- and acyloxy-alkyloxy analogues (3.601 and 3.910 A, respectively). For spirosulfurane 3 a rearrangement into the isomeric ten-membered cyclic anhydride 13 is observed.