Crystal and molecular structure of diastereomeric 2-diphenylthiophosphinoyl-cis-(4,6-dimethyl)-1,3-dithianes

The crystal and molecular structures of a pair of diastereomeric 2-diphenylthiophosphinoyl-cis-(4,6-dimethyl)-1,3-dithianes 2 have been determined by the X-ray method. The differences in corresponding bond distances in cis-2 and trans-2 are discussed in context of the anomeric effect operating in this heterocyclic system. The comparison of selected structural parameters between diastereomeric cis- and trans-dithianes 2 and their 5-t-butyl analogs 1 is also discussed. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:537–541, 1998     

Crystal structures of 2-ferrocenylmethylidenehydrazono-1,3-dithiane and 2-ferrocenylmethylidenehydrazono-1,3-dithiepane

Two compounds of 2-ferrocenylmethylidenehydrazono-1,3-dithiane (1) and 2-ferrocenylmethylidenehydrazono-1,3-dithiepane (2) are synthesized and their single crystal structures are determined by the X-ray diffraction method. Compound 1 belongs to the orthorhombic Pca2₁ space group with the cell parameters: a = 13.989(4) Å, b = 5.785(2) Å, c = 18.231(5) Å, V = 1475.4(7) ų; while compound 2 crystallizes in a monoclinic symmetry, P2₁/c space group with a = 15.320(2) Å, b = 5.8028(6) Å, c = 36.584(4) Å, β = 91.932(1)° and V = 3250.4(6) ų.     

The anomeric effect in 2-arylseleno-1,3-dithianes

The anomeric effect in a series of 2-(4-substituted-phenylseleno)-1,3-dithianes (substituents, R = NO₂, CF₃, H, OMe, NMe₂) decreases in the sequence NO₂>CF₃>H>OMe>NMe₂, providing systematic experimental evidence for the role of stabilizing orbital interactions.     

Rotation and inversion barriers in 2-lithio-2-phenyl-1,3-dithianes

The barriers to phenyl rotation in 2-lithio-2-phenyl-cis-4,6-dimethyl-, 2-lithio-2-phenyl-4,4,6-trimethyl- and 2-lithio-2-phenyl-trans-4,6-dimethyl-1,3-dithiane are compared in tetrahydrofuran (THF) and hexamethylphosphortriamide (HMPA). In the first two cases, the barriers in THF are lower than those in HMPA, presumably because the lithio compound exists as a tight ion pair in THF but as a solvent-separated ion pair (with more delocalization of charge into the phenyl ring) in HMPA. However, in the trans-4,6-dimethyl compound the barriers are the same in the two solvents and nearly equal to the barriers for ring reversal. It is concluded that in this compound the rate-determining step for phenyl rotation may actually be ring reversal, at least in solvent HMPA.     

Unexpected reactivity of oxygenated 2-acyl-1,3-dithianes with electrophiles

Lithium enolates of oxygenated acyl-dithiane undergo unexpected regiospecific reactions with electrophiles. Reaction of aldehydes with oxygenated acyl-dithiane leads to the formation of the corresponding monosubstituted β-hydroxy-acyl-dithiane.     

Study of the anomeric effect in 2-substituted 1,3-dithianes

The conformational analysis of several 2-substituted 1,3-dithianes made possible the evaluation of S-C-Y anomeric interactions, where Y = SCH₃, SC₆H₅, CO₂CH₃, CO₆H₅, CO₂H and N(CH₃)₂. The relative magnitude of the effects observed for these groups [ΔG°_dithiane(Y) - ΔGδ _cyclohexane(Y)] can be explained in terms of the combined influence of dipole/dipole and two-electron stabilizing interactions (stereoelectronic effect).     

The molecular and crystal structures of two diastereomeric 3,4-dihydropyrromethenones

The molecular and crystal structures of the two racemic diastereomeric 3,4-dihydropyrromethenone derivatives1 and2 of configurations (Z) and (E) were determined at 93 K (1, 2) and at room temperature (1). From an analysis of the crystallographically observed temperature coefficients a pseudorotation flexibility of the pyrrolidinone ring in the crystal is deduced. In both compounds a nearly orthogonal arrangement between the two heterocyclic ring systems is observed, which is ascribed to the steric bulk of the substituents in positions 1 and 3 of the pyrrolidinone ring.Herrn Prof.Josef Schurz zum 60. Geburtstag gewidmet.     

A new synthesis of 2-substituted-1,3-dithianes from trichloromethyl compounds

Trichloromethyl compounds are efficiently converted into 1,3-dithianes upon reaction with a disodium 1,3-propanedithiolate-1,3-propanedithiol mixture in DMF solution at 0 °C. This synthesis is limited to those substrates where the substituent attached to the trichloromethyl group is an electron-withdrawing group.     

Reacton of Representative 2-Acyl-1,3-dithianes with Alkylating and Acylating Agents

2-cyclohexanoyl-1,3-dithiane 2, a representative 2-acyl-1,3-dithianes, reacts with various alkylating and acylating agents affording masked polycarbonyl coumpounds.     

Crystal and molecular structure of 5,5-dichlormethyl-2-phenyl-1,3-dioxane

All-Union Scientific-Research Institute of Chemical Reagents and Ultrapure Chemical Substances. Ufa Petroleum Institute. Translated from Zhurnal Strukturnoi Khimii, Vol. 29, No. 4, pp. 149–153, July–August, 1988.     

Deprotection of thioacetals and 1,3-dithianes with dimethylsulphoxide

The dialkylthioacetals, cyclic ethanediylthioacetals and 1,3-dithianes are shown to undergo facile dethioacetalization on heating in dimethylsulphoxide under neutral conditions to afford the corresponding carbonyl compounds in good yields.     

NMR spectral analysis of 1,3,2-dithiaphosphorinanes and 1,3-dithianes

The full set of NMR spectral parameters (¹H, ¹³C, ³¹P) are reported for 2-phenyl-1,3,2-dithiaphosphorinane and 2-phenyl-1,3-dithiane. The stereochemical dependence of the coupling constants is discussed.     

Selective desulfurization of 1,3-dithianes, -oxathiolanes and -thiazolidines by tributyltin hydride

Selective desulfurization of 2-alkyl-1,3-dithianes, -oxathiolanes, or -thiazolidines 1 with one equivalent of tri-n-butyltin hydride yields acyclic compounds R¹R²CHX(CH₂)_nSSnBu₃ (X = S,O,NH; N= 2,3), (2) which can be destannylated to the corresponding mercaptans 3.     

Electron impact mass spectrometry of some 2-methyl-2-aryl- and 2-methyl-2-alkyl-1,3-dithianes

The electron impact mass spectrometric behaviour of four 2-methyl-2-aryl- and two 2-methyl-2-alkyl-1,3-dithianes is described and discussed in detail, with the aid of exact mass measurements, linked scans and mass-analysed ion kinetic energy spectrometry. The mechanism of the primary HS₂˙ loss, as well as those of the more unusual fragmentation pathways, are given.     

Reactions of nitrile oxides with 2-lithio-1,3-dithianes synthesis of α-diketones

Nitrile oxides (2) were treated with 2-lithio-1,3-dithianes (4) to give in good yields masked ketoximes (5), new synthetic tools for a α-diketones.     

Chemical ionization and electron impact mass spectra of alicyclic substituted 2-aryl-1,3-dithianes

The methane and isobutane chemical ionization mass spectra of alicyclic substituted 2-aryl-1,3-dithianes were examined by gas chromatography mass spectrometry. The protonated molecular ion was found to be of low abundance in the methane spectra, while a protonated cyclic sulfide cation (m/z 107) appeared as the base peak. A protonated molecular ion was the base peak when isobutane was used as the reagent gas. Electron impact mass spectra displayed weak molecular ions and were characterized by the m/z 106 fragment.