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The single‐crystal X‐ray structure determinations of the title complexes, cis‐di­chloro‐trans‐di­methyl‐cis‐bis(N‐methyl­pyr­rolidin‐2‐one‐O)­tin(IV), [Sn(CH3)2Cl2(C5H9NO)2], cis‐di­bromo‐trans‐di­methyl‐cis‐bis(N‐methyl­pyrrolidin‐2‐one‐O)tin­(IV), [SnBr2(CH3)2(C5H9NO)2], and cis‐di­iodo‐trans‐di­methyl‐cis‐bis(N‐methyl­pyrrolidin‐2‐one‐O)­tin(IV), [Sn(CH3)2I2(C5H9NO)2], show that those tin complexes in which coordination of the lactam ligand to SnIVis realized viaoxygen exhibit a distorted octahedral geometry.

The preparation and X‐ray analysis of the title compound, [Sn2Br4(CH3)4(C5H9NO)], are described. The compound contains two Sn atoms in the asymmetric unit, that complexed by N‐methyl­pyrrolidin‐2‐one being hexacoordinated (a), the other exhibiting pentacoordination (b). The most important features are three different Sn—Br bond lengths at both Sn atoms with the following values: (a) 2.5060 (9), 2.7152 (10) and 3.7118 (10) Å; (b) 2.5084 (10), 2.5279 (9) and 3.5841 (10) Å.

The synthesis and X‐ray structure analysis of the title compound, [SnBr2(CH3)2(C4H9NO)2], are described. The crystal contains mol­ecules which are separated by normal van der Waals distances. Organotin(IV) compounds are found in a variety of structural types, in which the Sn atom can, for example, be hexacoordinated. In this case, the preferred solid‐state molecular structure of the central atom is octahedral. The degree of distortion and the configuration depend on the ligands.

The synthesis and the X‐ray structural analysis of the title compound, μ‐chloro‐1:2κ2Cl‐tri­chloro‐1κCl,2κ2Cl‐tetra­methyl‐1κ2C,2κ2C‐(N‐methyl­pyrrolidin‐2‐one)‐1κO‐ditin(IV), [Sn2Cl4(CH3)4(C5H9NO)], are described. The title compound is found to exhibit a distorted trigonal–bipyramidal geometry at both SnIVatoms. The Sn—Cl—Sn angle involving the bridging chlorine ligand is 135.56 (5)°, with the Sn—Cl bond lengths being 2.5704 (13) and 3.1159 (13) Å.

The title compound, di‐μ‐chloro‐bis{[(2,3,4‐η)‐ethyl 6,6‐di­methyl‐5‐oxohept‐2‐enoato]­palladium(II)}, [Pd2Cl2(C11­H17­O3)2], is a binuclear chloro‐bridged palladium allyl complex that was obtained serendipitously From the reaction of 6,6‐di­methyl‐2‐hepten‐4‐ynoate with Na2PdCl4in water‐containing alcohol. The allyl group is substituted with an ester and a tert‐butyl­carboxy group. The dimeric mol­ecules link viaC—H⃛O contacts into a two‐dimensional network parallel to the bcplane.

The title compound, di­bromo­di­methyl(N‐methyl­pyrrolidin‐2‐one‐O)­tin(IV), [SnBr2(CH3)2(C5H9NO)], exhibits pentacoordination of the Sn atom, with long and short Sn—Br bonds [2.6737 (4) and 2.5256 (4) Å, respectively]. The distorted trigonal–bipyramidal coordination polyhedron has two methyl groups and one Br atom in the equatorial plane, the second Br atom and the N‐methyl­pyrrolidinone (NMP) ligand occupying the apical positions.

Esterification of a single diastereomer of 2‐(4‐methylene­cyclohex‐2‐enyl)propanol, (II), with (1R,4S)‐(+)‐camphanic acid [(1R,4S)‐4,7,7‐trimethyl‐3‐oxo‐2‐oxabicyclo[2.2.1]heptane‐1‐carboxylic acid] leads to the crystalline title compound, C20H28O4. The relative configuration of the camphanate was determined by X‐ray diffraction analysis. The outcome clarifies the relative and absolute stereochemistry of the naturally occurring bisabolane sesquiterpenes β‐turmerone and β‐sesquiphellandrene, since we have converted (II) into both natural products viaa stereospecific route.

Stereoselective hydroboration of (−)‐isopulegol and subsequent fractional crystallization furnishes the title compound, C10H20O2. The relative configuration of the stereogenic centres has been assigned by means of X‐ray diffraction analysis since the monoterpenediol is employed as a versatile chiral building block in stereospecific natural product synthesis.

The synthesis and crystal structure analysis viaX‐ray diffraction of the title compound, C20H24O4, (I), are described. The title compound is an androstadione bearing a diene in the Aand Brings [Krause & Thorand (1999). Inorg. Chim. Acta, 296, 1–11]. The diene conjugates with the carbonyl group. Intermolecular H⃛O contacts (2.53 and 2.64 Å; C—H⃛O angles 161 and 158°) indicate hydrogen bonds.

The title compound, C12H16O4, (I), was prepared by oxidation of (5S*,6R*)‐1,7‐di­oxa­di­spiro­[4.0.4.4]­tetra­decane‐2,8‐diol us­ing silver(I) carbonate and posesses a cisconfiguration of the two five‐membered‐ring lactones fused spiro to the six‐membered carbocycle, which has a chair conformation. It represents an exceptional structure for bis‐tetra­hydro­furan units, which are interesting building blocks in natural products. The synthesis, spectroscopic data and X‐ray structural analysis are described. The crystal contains discrete mol­ecules separated by normal van der Waals distances.

The synthesis, spectroscopic data and X‐ray structural analysis of the title compound, C26H35NO2S, (I), are described. The crystal contains discrete mol­ecules separated by normal van der Waals distances. The benzene­sulfon­amide derivative of the corresponding amine allows the assigment of its relative configuration. The secondary amine has been synthesized viaa sequential multi‐step hydro­formyl­ation procedure according to Eilbracht et al.[Chem. Rev.(1999), 99, 3329–3365].).

The crystal structure of the title compound, C10H20O2, was published [Körner et al.(2000). Acta Cryst. C56, 74–75] with an erroneous position for an hydroxy H atom. This has now been corrected and leads to a more sensible hydrogen‐bonding scheme.

The title compound, C16H26O2, (I), prepared by oxidation of (1R*,11R*)‐12‐hydroxy­bi­cyclo­[9.4.1]­hexa­decan‐16‐one using pyridinium dichromate, has a transconfiguration of the two fused rings and represents an interesting precursor for the synthesis of macrocyclic structures.

The title compound, C23H19N2O3P, was prepared by the reaction of ethynyldi­phenyl­phosphine oxide with phenyl isocyanate, triethyl­amine and nitoethane in benzene. The molecular structure is stabilized by an intramolecular N—H⋯O hydrogen bond.