Attempted 1,3-trimethylsilyl migration in Me3Si?PSN?R system

A dimer of thioxo-N-t-butylimino(trimethylsiloxy)-phosphorane 5 has been prepared by reaction of tris(trimethylsilyl) phosphine with N-sulfinyl-N-tert-butylamine. The structure of 5 has been confimed by X-ray analysis data. 1-Aza-2-thia-3-phosphaallene 1 , thiaphosphaziridine 3 , iminophosphine P-sulfide 4 are postulated as intermediates of the reaction studied.     

N-alkyl-C-polyfluoroalkyl-C-chlorosulfinimides RFC(Cl)SN?R

The N-alkyl-C-polyfluoroalkyl-C-chlorosulfinimides R_FC(Cl)SN R have been investigated. Some aspects of their thermal stability and their [3 + 2] and [3 + 1] cycloaddition reactions have been examined.     

Heterocyclizations of hydroxyketones with two‐coordinated (trimethylsilylamino)phosphines, (Me3Si)2N?PE?SiMe3

The reaction of two‐coordinated (trimethylsilylamino)phosphines (Me₃Si)₂N PE SiMe₃ 1 (E = N) and 2 (E = CH) with hydroxycarbonyl compounds proceeded with four‐ or five‐member heterocyclization to yield derivatives of oxaphosphetane, oxaphospholanes, and oxaphospholes. The reaction rate depends on the structure of hydroxyketones as well as on the type of the two‐coordinated phosphorus compound in accordance with the polarity of the P=N and P=C bonds. Thus, reaction was completed in 30 min in the case of the ortho carbonyl phenoxy derivatives with the phosphine 1 , but required 2 h in the case of the alkyl hydroxy carbonyls. All reactions with the phosphine 2 took about 24 h. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:413–417, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20033     

Characterization of the N?H···ON and N?H···NO H‐bonds in nitrosamine dimers

Ab initio molecular orbital and DFT calculations have been carried out for three most stable dimers of parent nitrosamine (NA) in order to elucidate the structures and energetics of the dimers. The structures were optimized using HF, B3LYP, and MP2 methods with 6‐311+G(d,p) and 6‐311++G(2d,2p) basis sets. At the optimized geometries obtained at MP2/6‐311++G(2d,2p) level of theory, the energies were evaluated at QCISD/aug‐cc‐pVDZ and CCSD/aug‐cc‐pVDZ levels. The most stable dimer has two N? H···O?N hydrogen bonds and the least stable dimer has two N? H···N?O hydrogen bonds. The natural bond orbital analysis showed that the lpO(N) → BD*(N? N) and lpO(N) → BD*(N? H_b) interactions play a decisive role in the stabilization of the NH···O(N) hydrogen bonds in dimers. The atoms in molecules results reveal that the intermolecular N? H···O(N) H‐bonds in dimers have electrostatic character. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Does a Stabilising Interaction Favouring the Z,Z Configuration of ?S‐NSN‐S? Systems Exist?

The existence of the orbital interaction presented in the literature as being the cause for the stabilisation of the Z,Z configuration of Ph-S-N=S=N-S-Ph (1) and its derivatives in the crystal phase, has been investigated. The results of theoretical calculations at the DFT/B3LYP/6-311+G* level of theory suggest that such a stabilising interaction might not exist or be extremely weak and that packing forces must be the main cause of the observed Z,Z configuration in the solid. To reach this conclusion structural and energetic parameters were combined to study the bonding in these -S-N=S=N-S- systems. For the analogous Ph-Se-N=S=N-Se-Ph (2) in particular the isomeric equilibrium in solution found in the variable-temperature 77Se NMR spectrum indicates that, in the gas phase or in solution, the observed Z,Z configuration is not stabilised to a greater extent than the Z,E configuration.     

Mixed (PS/PO)‐Stabilized Geminal Dianion: Facile Diastereoselective Intramolecular C?H Activations by a Related Ruthenium–Carbene Complex

A new unsymmetrical geminal dianion that contained both a phosphine oxide moiety and a phosphine sulfide moiety has been synthesized. Its reactivity towards Ru^II was explored, which led to the formation of a highly reactive carbene complex that evolved at room temperature to yield a kinetic orthometalated Ru^II complex through C? H activation of the phenyl group of the phosphine oxide moiety. This insertion was found to be thermally reversible and a second C? H insertion occurred at a phenyl group of the phosphine sulfide moiety to form the thermodynamic orthometalated Ru^II complex in a diastereospecific manner. DFT calculations fully rationalized the experimental findings in terms of the relative energies of the kinetic and thermodynamic products and allowed the mechanism of this process to be fully understood.     

Fluorsulfonylmethylidene sulfur difluoride oxide,FSO2?CH  SF2  O

SO₃ adds across the CS double bond of H₂C  SF₄ with formation of 2-tetrafluoro-4-dioxo-1,2,4-oxadithietane, which rearranges to fluorsulfonylmethylidene sulfur difluoride oxide, F SO₂ CH  SF₂  O in the presence of CsF. © John Wiley & Sons, Inc.     

Homolytic S?S Bond Dissociation of 11 Bis(thiocarbonyl)disulfides R‐C(S)?S?S?C(S)R and Prediction of A Novel Rubber Vulcanization Accelerator

The structures and energetics of eight substituted bis(thiocarbonyl)disulfides (RCS₂)₂, their associated radicals RCS₂^., and their coordination compounds with a lithium cation have been studied at the G3X(MP2) level of theory for R=H, Me, F, Cl, OMe, SMe, NMe₂, and PMe₂. The effects of substituents on the dissociation of (RCS₂)₂ to RCS₂^. were analyzed using isodesmic stabilization reactions. Electron‐donating groups with an unshared pair of electrons have a pronounced stabilization effect on both (RCS₂)₂ and RCS₂^.. The S? S bond dissociation enthalpy of tetramethylthiuram disulfide (TMTD, R=NMe₂) is the lowest in the above series (155 kJ mol^?1), attributed to the particular stability of the formed Me₂NCS₂^. radical. Both (RCS₂)₂ and the fragmented radicals RCS₂^. form stable chelate complexes with a Li⁺ cation. The S? S homolytic bond cleavage in (RCS₂)₂ is facilitated by the reaction [Li(RCS₂)₂]⁺+Li⁺→2 [Li(RCS₂)]^.+. Three other substituted bis(thiocarbonyl) disulfides with the unconventional substituents R=OSF₅, Gu¹, and Gu² have been explored to find suitable alternative rubber vulcanization accelerators. Bis(thiocarbonyl)disulfide with a guanidine‐type substituent, (Gu¹CS₂)₂, is predicted to be an effective accelerator in sulfur vulcanization of rubber. Compared to TMTD, (Gu¹CS₂)₂ is calculated to have a lower bond dissociation enthalpy and smaller associated barrier for the S? S homolysis.     

The ?NH?(C)?Br functionality of heteroaromatic compounds as a synthon for fused dihydrooxazoles

Fused dihydrooxazoles are produced by the reaction of 8‐bromoteophylline (1), 6‐bromo‐2‐pyridone (7), or 2‐bromobenzimidazole (11) with an N‐substituted N‐(2,3‐epoxypropyl)amine. The product derived from 1 undergoes rearrangement to a fused dihydrooxazine while the fused dihydrooxazoles derived from 7 and 11 are stable. J. Heterocyclic Chem., (2011).     

Manganese‐Catalyzed Dehydrogenative [4+2] Annulation of N?H Imines and Alkynes by C?H/N?H Activation

Described herein is a manganese‐catalyzed dehydrogenative [4+2] annulation of N H imines and alkynes, a reaction providing highly atom‐economical access to diverse isoquinolines. This transformation represents the first example of manganese‐catalyzed C H activation of imines; the stoichiometric variant of the cyclomanganation was reported in 1971. The redox neutral reaction produces H₂ as the major byproduct and eliminates the need for any oxidants, external ligands, or additives, thus standing out from known isoquinoline synthesis by transition‐metal‐catalyzed C H activation. Mechanistic studies revealed the five‐membered manganacycle and manganese hydride species as key reaction intermediates in the catalytic cycle.     

Electronic structure of cations X ?OH (XC,N,O)

RHF(UHF)+MP2 and CASSCF calculations of potential energy surfaces' sections of cations X  OH (XC,N,O) and corresponding neutral particles are performed. It is shown that all cations should be relatively stable both with respect to X  O bond breaking and intramolecular rearrangements. Reactions of electron capture by these cations are also studied. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 77: 580–588, 2000     

Theoretical prediction regarding structural and thermodynamical characteristics of stable CH3PO2 isomers and unimolecular decomposition mechanisms of species CH3P(O)2, CH3O?PO,and CH2P(O)OH

The detailed isomerization and dissociation reaction potential energy profile of the CH₃PO₂ system was established at the UCCSD(T)/6‐311++G(3df,2p)//UB3LYP/6‐311++G(d,p) level of theory. Seventy minimum isomers were located and connected by 93 optimized interconversion transition states. Furthermore, 32 isomers with high kinetic stability were predicted to be possible candidates for further experimental detection. The bonding nature of the suggested stable isomers was analyzed while their molecular properties including heats of formation, adiabatic ionization potentials, and adiabatic electronic affinities were calculated at the G2, G2(MP2), G3, and CBS‐Q levels. Based on the isomerization and dissociation potential energy surface, possible unimolecular decomposition mechanisms and pathways of the low‐lying molecules CH₃P(?O)₂, CH₃O? P?O, and CH₂?P(?O)OH were discussed. Furthermore, the transition state theory rate constants of the primary unimolecular dissociation channels were also calculated. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009     

Investigation on the individual contributions of N?H···OC and C?H···OC interactions to the binding energies of β‐sheet models

In this article, the binding energies of 16 antiparallel and parallel β‐sheet models are estimated using the analytic potential energy function we proposed recently and the results are compared with those obtained from MP2, AMBER99, OPLSAA/L, and CHARMM27 calculations. The comparisons indicate that the analytic potential energy function can produce reasonable binding energies for β‐sheet models. Further comparisons suggest that the binding energy of the β‐sheet models might come mainly from dipole–dipole attractive and repulsive interactions and VDW interactions between the two strands. The dipole–dipole attractive and repulsive interactions are further obtained in this article. The total of N? H···H? N and C?O···O?C dipole–dipole repulsive interaction (the secondary electrostatic repulsive interaction) in the small ring of the antiparallel β‐sheet models is estimated to be about 6.0 kcal/mol. The individual N? H···O?C dipole–dipole attractive interaction is predicted to be ?6.2 ± 0.2 kcal/mol in the antiparallel β‐sheet models and ?5.2 ± 0.6 kcal/mol in the parallel β‐sheet models. The individual C^α? H···O?C attractive interaction is ?1.2 ± 0.2 kcal/mol in the antiparallel β‐sheet models and ?1.5 ± 0.2 kcal/mol in the parallel β‐sheet models. These values are important in understanding the interactions at protein–protein interfaces and developing a more accurate force field for peptides and proteins. © 2009 Wiley Periodicals, Inc. J Comput Chem 2010     

Resolving the enigma of prebiotic C?O?P bond formation: Prebiotic hydrothermal synthesis of important biological phosphate esters

Important biological phosphate esters such as sn‐glycerol‐3‐phosphate, glycerol‐2‐phosphate, and phosphoethanolamine were synthesized under hydrothermal conditions. Phosphorus was incorporated into the biomolecules, leading to the formation of C O P type compounds hydrothermally. Only perlite‐catalyzed reaction at 180°C could result in the formation of sn‐glycerol‐3‐phosphate, whereas glycerol‐2‐phosphate could be easily synthesized at 100°C with or without minerals and phosphoethanolamine was obtained within a temperature range of 100 to 120°C. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:161–167, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20591     

Methylidene Rare‐Earth‐Metal Complex Mediated Transformations of CN,NN and N?H Bonds: New Routes to Imido Rare‐Earth‐Metal Clusters

Three new patterns of reactivity of rare‐earth metal methylidene complexes have been established and thus have resulted in access to a wide variety of imido rare‐earth metal complexes [L₃Ln₃(μ₂‐Me)₃(μ₃‐Me)(μ ‐ NR)] (L=[PhC(NC₆H₃iPr₂‐2,6)₂]^?; R=Ph, Ln=Y ( 2 a ), Lu ( 2 b ); R=2,6‐Me₂C₆H₃, Ln=Y ( 3 a ), Lu ( 3 b ); R=p‐ClC₆H₄, Ln=Y ( 4 a ), Lu ( 4 b ); R=p‐MeOC₆H₄, Ln=Y ( 5 a ), Lu ( 5 b ); R=Me₂CHCH₂CH₂, Ln=Y ( 6 a ), Lu ( 6 b )) and [{L₃Lu₃(μ₂‐Me)₃(μ₃‐Me)}₂(μ ‐ NR′N)] (R′=(CH₂)₆ ( 7 b ), (C₆H₄)₂ ( 8 b )). Complex 2 b was treated with an excess of CO₂ to give the corresponding carboxylate complex [L₃Lu₃(μ‐η¹:η¹‐O₂CCH₃)₃(μ‐η¹:η²‐O₂C‐CH₃)(μ‐η¹:η¹:η²‐O₂CNPh)] ( 9 b ) easily. Complex 2 a could undergo the selective μ₃‐Me abstraction reaction with phenyl acetylene to give the mixed imido/alkynide complex [L₃Y₃(μ₂‐Me)₃(μ₃‐η¹:η¹:η³‐NPh)(μ₃‐C?CPh)] ( 10 a ) in high yield. Treatment of 2 with one equivalent of thiophenol gave the selective μ₃‐methyl‐abstracted products [L₃Ln₃(μ₂‐Me)₃(μ₃‐η¹:η¹:η³‐NPh)(μ₃‐SPh)] (Ln=Y ( 11 a ); Lu ( 11 b ). All new complexes have been characterized by elemental analysis, NMR spectroscopy, and most of the structures confirmed by X‐ray diffraction.     

Intramolecular Aminocyanation of Alkenes by N?CN Bond Cleavage

A metal‐free, Lewis acid promoted intramolecular aminocyanation of alkenes was developed. B(C₆F₅)₃ activates N‐sulfonyl cyanamides, thus leading to a formal cleavage of the N CN bonds in conjunction with vicinal addition of sulfonamide and nitrile groups across an alkene. This method enables atom‐economical access to indolines and tetrahydroquinolines in excellent yields, and provides a complementary strategy for regioselective alkene difunctionalizations with sulfonamide and nitrile groups. Labeling experiments with ¹³C suggest a fully intramolecular cyclization pattern due to the lack of label scrambling in double crossover experiments. Catalysis with Lewis acid is realized and the reaction can be conducted under air.