Heteroatom Chemistry

Kassaee, M. Z.; Musavi, S. M.; Soleimani‐Amiri, S.; Ghambarian, M.

doi: 10.1002/hc.20204pmid: N/A

With the aim of recognizing the steric effects on the silylenic H2C2Si structures, ab initio and DFT calculations are carried out on 24 structures of X2C2Si (where X is hydrogen (H), methyl (Me), isopropyl (i‐pro), and tert‐butyl (tert‐Bu)). These species are at either triplet (t) or singlet (s) states. They are confined to the following three sets of structures (1X, 2X and 3X). Structures 1X include silacyclopropenylidenes (1s‐H and 1t‐H) and their 2,3‐disubstituted derivatives (1t‐Me, 1s‐Me; 1t‐i‐pro, 1s‐i‐pro; 1t‐tert‐Bu, 1s‐tert‐Bu). Structures 2X include vinylidenesilylenes (2s‐H and 2t‐H) and their 3,3‐disubstituted derivatives (2t‐Me, 2s‐Me; 2t‐i‐pro, 2s‐i‐pro; 2t‐tert‐Bu, 2s‐tert‐Bu). Structures 3X include ethynylsilylenes (3s‐H and 3t‐H) and their 1,3‐disubstituted derivatives (3t‐Me, 3s‐Me; 3t‐i‐pro, 3s‐i‐pro; 3t‐tert‐Bu, 3s‐tert‐Bu). Singlet–triplet energy separations (Δ Es‐t, X) and relative energies for the above structures are acquired at HF/6‐31G*, B1LYP/6‐31G*, B3LYP/6‐31G*, MP2/6‐31G*, HF/6‐31G**, B1LYP/6‐31G**, B3LYP/6‐31G**, and MP2/6‐31G** levels of theory. The highest Δ Es‐t, X is encountered for 1X. All singlet states of X2C2Si, are more stable than their corresponding triplet states. Linear correlations are found between the LUMO–HOMO energy gaps of the singlet 1s‐X and 2s‐X with their corresponding singlet–triplet energy separations calculated at B3LYP/6‐31G**. The seven structures 2s‐Me, 2t‐Me, 3s‐Me, 1t‐Me, 1s‐Me, 1s‐tert‐Bu, and 3t‐tert‐Bu do not appear to be real isomers. Different stability orders are obtained as a function of the substituents (X). The order of stability for six isomers of H2C2Si is 1s‐H > 2s‐H > 3s‐H > 2t‐H > 3t‐H > 1t‐H. Replacing hydrogen atoms by methyl group (X = Me) presents a new stability order: 1s‐Me > 3s‐Me > 2s‐Me > 3t‐Me > 2t‐Me > 1t‐Me; and for (i‐pro)2C2Si is 1s‐i‐pro > 2s‐i‐pro ≈ 3s‐i‐pro > 3t‐i‐pro ≈ 2t‐i‐pro > 1t‐i‐pro. Using the larger tert‐butyl group as a substituent (X), yet it offers a more different stability order for six structures of (tert‐Bu)2C2Si: 1s‐tert‐Bu > 3s‐tert‐Bu > 2s‐tert‐Bu > 3t‐tert‐Bu > 1t‐tert‐Bu > 2t‐tert‐Bu. Among eight levels employed, B3LYP/6‐31G** appears as the method of choice. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:619–633, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20204

Al‐Raqa, Shaya Y.; ElSharief, Ahmed M. Sh.; Khalil, Saied M. E.; Al‐Amri, Abdulkhaliq M.

doi: 10.1002/hc.20244pmid: N/A

Halogenated imidazo(pyrazine,(1,4)diazocine and quinoxaline), 9,10‐anthraquinone‐ (6,7‐e), phenanthroline(5,6‐e) {imidazo(4,5‐b)pyrazine}, and naphtho(1,8‐ef)imidazo(4,5‐b)(1,4) diazipen were obtained through interaction of imidazolidineiminothiones with the corresponding diamino compounds. Imidazo(4,5‐e) triazine and pyrrolo(2,3‐d)imidazole were prepared when the iminothiones were reacted with thiocarbohydrazide and with ethylphenyl acetate, separately. Some of the synthesized compounds exhibited better biological and antitumor activities. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:634–647, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20244

Magyarosy, Andrew; Mohareb, Rafat M.; Ho, Jonathan Z.

doi: 10.1002/hc.20249pmid: N/A

A new method for linear polymerization of maleimides via the Diels–Alder reaction has been developed. This method involves use of a new cross‐linking agent, benzene‐3,4‐dimethylenesuccinimide, which can be generated in situ from its thiophene precursor, benzene‐2,5‐dihydrothiophene‐3,4‐dicarboximide‐S,S‐dioxide. This new cross‐linking agent is reasonably reactive, readily prepared, and stable at room temperature. A controlled molecular weight oligomer has been synthesized and applied to the polymerization to yield a highly thermal stable polyimide. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:648–652, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20249

Prakash, Om; Kumar, Rajesh; Sharma, Deepak; Naithani, Rajesh; Kumar, Ravi

doi: 10.1002/hc.20250pmid: N/A

Oxidation of bis‐2,4‐pyrimidinylhydrazones of various araldehydes with two equivalents of iodobenzene diacetate in dichloromethane provides an efficient and easy method for the synthesis of eight new 3,9‐diaryl‐bis‐1,2,4‐triazolo(4,3‐a)(4,3‐c)pyrimidines. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:653–655, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20250

Beganskiene, Aldona; Nikishkin, Nicolai I.; Luck, Rudy L.; Urnezius, Eugenijus

doi: 10.1002/hc.20251pmid: N/A

Compounds bearing the structural motif of 2,6‐bis(phosphino)phenol have been synthesized via two general methods. Double lithium‐halogen exchange occurred in low‐temperature reactions of O‐protected (by methyl‐ or tetrahydropyranyl groups) 2,6‐dibromo‐4‐methylphenol derivatives with BuLi (2 equivalents); quenching the reaction mixtures with chlorophosphines ClPR2 (R = Ph, iPr) and corresponding O‐deprotection yielded symmetrically substituted 2,6‐bis(phosphino)phenols. Sequential incorporation of PR2 functionalities was accomplished via single lithium‐halogen exchange (1 eq. of BuLi) of tetrahydropyranyl‐protected 2,6‐dibromo‐4‐methylphenol followed by ClPR2 quenches, thus enabling the syntheses of unsymmetric 2,6‐bis(phosphino)phenols. Such compounds were also obtained via sequential ortho‐lithiations of tetrahydropyranyl‐protected 4‐tert‐but ylphenol, followed by ClPR2 quenches. All of the new compounds have been characterized by spectrometric methods (1H and 31P NMR, and mass spectrometry). In addition, two of the compounds, 1‐(diphenylphosphino)‐3‐(diphenylphosphoryl)‐2‐methoxy‐5‐methylbenzene (3a‐ox) and 1,3‐bis(diphenylphosphino)‐2‐methoxy‐5‐methylbenzene (6a) have also been characterized via single crystal X‐ray diffraction experiments. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:656–663, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20251

Li, Zheng; Yang, Jingya; Wang, Junke; Wang, Xicun

doi: 10.1002/hc.20253pmid: N/A

An efficient soluble poly(ethylene glycol) (PEG) supported liquid‐phase parallel synthetic method for 2,5‐disubstituted 1,3,4‐oxadiazoles and 1,3,4‐thiadiazoles is described. 2‐Aryl‐5‐(4′‐methoxycarbonylphenoxymethyl)‐1,3,4‐oxadiazoles and 2‐aryloxymethyl‐5‐(4′‐methoxycarbonylphenoxyacetamido)‐1,3,4‐thiadiazoles are synthesized in high yield and high purity using this polymer supported strategy. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:664–669, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20253

Nizamov, Il'yas S.; Bolshakova, Olga V.; Al'metkina, Lyubov A.; Nizamov, Il'nar D.; Sergeenko, Gulnur G.; Frolova, Liliya V.; Krivolapov, Dmitry B.; Batyeva, Elvira S.; Litvinov, Igor A.

doi: 10.1002/hc.20231pmid: N/A

S‐(Diethylamino)dimethylsilyl bis(diethylamido)dithiophosphate 3 was obtained by the reaction of tetraphosphorus decasulfide 1 with bis(diethylamino)dimethylsilane 2a. The reactions of Lawesson's reagent 5 with 2a and the alkyl homologues of Davy's reagent 8a,b with trimethyl(diethylamino)silane 6 were studied. On the basis of these reactions, methods of synthesizing S‐(diethylamino)dimethylsilyl or S‐(diethylamino)diphenylsilyl 4‐methoxyphenyl (diethylamido)dithiophosphonates 7a and 7b and S‐trimethylsilyl S‐alkyl(diethylamido)trithiophosphates 9a,b are described. The optimal reaction conditions and thermal stability of S‐trimethylsilyl S‐ethyl(diethylamido)trithiophosphate 9a were defined by differential thermal analyses. Compound 9a have been decomposed to form 2,4‐bis(diethylamido)‐1,3,2,4‐dithiadiphosphetane‐2,4‐disulfide 10 which structure was established by X‐ray single crystal diffraction. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:670–675, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20231

Przychodzeń, Witold

doi: 10.1002/hc.20259pmid: N/A

To explore the generality and scope of direct thionation of hydroxamic acids (HAs), the reaction of various structurally diverse HAs with Lawesson's reagent was investigated. The yield of thiohydroxamic acid (THAs) is poor when HAs possess bulky acyl and/or N‐substituents, acidic α‐hydrogen atoms, or an N‐phenyl ring. THAs yields were correlated with Brown sigma parameter. The relative rates of two subsequent processes k T 2 and k R 2 were also measured. Correlation was also found for methine proton chemical shifts of N‐isopropyl benzothiohydroxamic acids. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:676–684, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20259

Bonacorso, Helio G.; Oliveira, Marli R.; Costa, Michelle B.; Drekener, Roberta L.; Silva, Letícia B. da; Zanatta, Nilo; Martins, Marcos A. P.

doi: 10.1002/hc.20261pmid: N/A

The one‐step regiospecific synthesis of a novel series of 10 trichloromethyl‐, aryl‐, and heteroaroyl‐substituted 5‐hydroxy‐2‐pyrazolines affords 1‐(2‐thenoyl)‐, 1‐(2‐furoyl)‐, and 1‐(isonicotinoyl)‐3‐aryl‐5‐hydroxy‐5‐trichloromethyl‐4,5‐dihydro‐1H‐pyrazoles in 63–92% yields from the cyclocondensation reactions of 1,1,1‐trichloro‐4‐methoxy‐4‐aryl‐3‐buten‐2‐ones (where aryl substituents are –C6H5, 4‐CH3C6H4, 4‐OCH3C6H4, 4‐FC6H4, 4‐ClC6H4, 4‐BrC6H4) with 2‐thiophenecarboxylic hydrazide, furoic hydrazide, and isonicotinic acid hydrazide, respectively. Dehydration reaction of two 2‐pyrazolines with P2O5 furnished the corresponding 1H‐pyrazoles in low yields (21–29%). © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:685–691, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20261

Gupta, Sushil K.; Kelkar, Anoop

doi: 10.1002/hc.20238pmid: N/A

Treatment of anhydrous MCl2 (M = Mn, Fe) with (Ph2PMe2Si)3CH in toluene at elevated temperature resulted in the isolation of colorless (MnCl2{(Ph2PMe2Si)3CH}) (1) and light yellow (FeCl2{(Ph2PMe2Si)3CH}) (2) in high yield. These paramagnetic complexes have been characterized by elemental analyses, magnetic moment, conductivity measurements, TGA, cyclic voltammetry, mass spectrometry, with IR, electronic, ESR and Mössbauer spectroscopy. The data suggest that complexes 1 and 2 have trigonal bipyramidal geometry around the metal atom with tridentate coordination of the ligand. The thermal stability of the Fe(II) complex 2 is greater than that of the Mn(II) compound 1. Electrochemical studies of complex 1 and 2 using cyclic voltammetry indicate a quasi‐reversible reduction (E1/2 = ca. −1.08 V (1)) and an irreversible cathodic reduction (Epc, ca. −1.55 V (2)) to Mn(0) and to Fe(0), respectively. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:692–698, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20238