(Z,Z)-2,3-bis(trimethylsilyl)-1,4-dibromo- and 2,3-bis(trimethylsilyl)-1,1,4,4-tetrabromobuta-1,3-dienes. Synthesis and Diels-Alder reactions.

The two title compounds (1,2) have been prepared and some Diels-Alder reactions investigated.     

Synthesis of beta-, gamma-, and delta-lactams via Pd(II)-catalyzed C-H activation reactions

Pd(II)-catalyzed intramolecular amination of sp2 and sp3 C-H bonds are developed using a combination of CuCl2 and AgOAc as the oxidant. The reaction protocol tolerates the presence of a double bond in the substrates. This catalytic reaction provides practical access to a wide range of beta-, gamma-, and delta-lactams.     

Synthesis of 1,2-bis(methoxyamino)cycloalkanes from alicyclic 1,2-bis(hydroxyamines)

Derivatives of 1,4-dihydroxypiperazine-2,3-dione were obtained by reaction of cis-1,2-bis(hydroxyamino)cycloalkanes with diethyl oxalate. Their alkylation with CH₂N₂ or Mel afforded 1,4-dimethoxypiperazine-2,3-diones. Hydrolysis of the latter gave 1,2-bis(methoxyamino)cycloalkanes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 925–929, April, 1996.     

Synthesis and reactivity of 1,2-bis(chlorodimethylgermyl)carborane and 1,2-bis(bromodimethylstannyl)carborane

The 1,2-bis(chlorogermyl)- (1) and 1,2-bis(bromostannyl)carborane (2) have been prepared by the reaction of dilithio-o-carborane with Me(2)GeCl(2) and Me(2)SnBr(2), respectively. Compounds 1 and 2 are found to be good precursors for the synthesis of a variety of cyclization compounds. The Wurtz-type coupling reaction of 1 and 2 using sodium metal afforded the four-membered digerma compound 3 and five-membered tristanna compound 4, respectively. The salt elimination reactions of 1 and 2 using Li(2)N(t)Bu and Li(2)PC(6)H(5) afforded the cyclic products [structure: see text]. The 1,2-bis(dimethylgermyl)carborane 9 and 1,2-bis(dimethylstannyl)carborane 10 were prepared by the reaction of 1 and 2 with sodium cyanoborohydride. The reactions of 9 and 10 with Pd(PPh(3))(4) afforded the bis(germyl)palladium 12 and bis(stannyl)palladium 13 complexes, respectively.     

Synthesis, structure, and some reactions of 1,2-bis(2-alkylthio-3-thienyl)perfluorocyclopentene

The synthesis of 1,2-bis(2-ethylthio-3-thienyl)perfluorocyclopentene is described. Metallation with n-BuLi and subsequent treatment with DMF or CO₂ gave the corresponding 5,5-diformyl and dicarboxy derivatives. The structure of 1,2-bis(2-ethylthio-3-thienyl)perfluorocyclopentene was studied by x-ray structural analysis. It was established that the unit cell contains two crystallographically independent molecules with geometrical and conformational parameters close to one another. The thiophene rings were inclined at an angle of 60° to the plane of the perfluorocyclopentene fragment, the thioalkyl groups were disposed antiparallel to it.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Moscow 117913. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 927–933, July, 1998.     

One-Pot Synthesis of N-Boc-2, 5-bis(trimethylsilyl)pyrrolidine

Since Daly reported the structure of epibatidine and its potent analgesic activity in 19921, study on the synthesis of epibatidine and its derivatives and relationships between the structure and activity of epibatidine has received much attention2. During the course of our research for the synthesis of epibatidine derivatives, N-boc-2, 5-bis(trimethylsilyl)pyrrolidine 4 was used as the key intermediate to construct the skeleton of epibatidine via the 1, 3-dipolar cycloaddition (Scheme 1). Ac…     

Synthesis of naphtho[b]cyclobutenes from 1,2-bis(3-propynol)benzenes

We have demonstrated that the reaction of benzene-bridged bis(propargyl alcohol)s with chlorodialkylphosphines exclusively afforded 3,8-bis(dialkylphosphinyl)naphtho[b]cyclobutenes via the [2+2] cycloaddition of 1,2-bis(α-phosphinylallenyl)benzenes. Dephosphinylation of the product has also been achieved.     

Crystal chemistry of protonated 1,2-bis(di-R-aminomethyl)benzenes. Part VI: 1,2-bis(diethylaminomethyl)-4,5-dichlorobenzene perchlorate

The crystals of a 1:1 complex of 1,2-bis(diethylaminomethyl)-4,5-dichlorobenzene perchlorate with HClO₄ were studied using X-ray diffraction and FT-IR spectroscopy. There are two symmetry-independent ionic pairs in the crystal, monoclinic, space group P2₁/n. In both symmetry-independent cations, the diethylaminomethyl substituents are in a similar Z conformation relative to the phenyl moieties, however significant conformational differences in the diethylaminomethyls have been noted. The diethylaminomethyls are linked by intracationic ⁺N–H⋯N hydrogen bonds of 2.758(9) and 2.721(7) Å in two symmetry-independent cations. The protons in these H-bonds are disordered in two off-center sites, which is most likely to be connected with the considerable disorder of the perchlorate anions. The IR spectrum of the crystals shows a broad intense band and a relatively intense continuous absorption indicating relatively large proton polarizability in the intramolecular hydrogen bond of a medium length.     

Synthesis of 1,2 difluoro-1,2-bis(pentafluorophenyl)dichlorane

1,2-Difluoro-1,2-bis(pentafluorophenyl)dichlorane is a new class of organic polyvalent chlorine compound. The closeness of the retention time of this compound and that of chloropentafluoro- benzene made its purification difficult. All attempts to obtain this compound in high yield have failed. 1,2-Difluoro-1,2-bis- (pentafluorophenyl)dichlorane is prepared by fluorination of chloropentafluorobenzene at 128°C with elemental fluorine. It has been characterized by ¹⁹F n.m.r., i.r., mass spectroscopy and elemental analysis.     

Preparation of 6,13-bis(trimethylsilyl)pentacene and formation of second-ring Diels-Alder adduct of pentacene

6,13-Bis(trimethylsilyl)pentacene was synthesized by a coupling reaction of bicyclic dilithiobutadiene with diiodonaphthalene followed by aromatization. Diels-Alder reaction of 6,13-bis(trimethylsilyl)pentacene with dienophiles afforded the corresponding second-ring adducts. Elimination of two silyl groups gave the second-ring Diels-Alder adducts of parent pentacene.     

Synthesis of Delta(1)-1,2-diazetines via a Diels-Alder cycloaddition approach

[reaction: see text] A novel method for the synthesis of Delta(1)-1,2-diazetines is presented. Diels-Alder cycloaddition of dienophile 4 with five dienes afforded cycloadducts in good to excellent yields. Four of the obtained cycloadducts were converted to the corresponding diazetines.     

Synthesis and inverse electron demand Diels-Alder reactions of 3,6-bis(3,4-dimethoxybenzoyl)-1,2,4,5-tetrazine

The synthesis of 3,6-bis(3,4-dimethoxybenzoyl)-1,2,4,5-tetrazine (2) and the scope of its reactivity in inverse electron demand Diels-Alder reactions are disclosed representing the first systematic study of the [4 + 2] cycloaddition reactions of 3,6-diacyl-1,2,4,5-tetrazines.     

Electrochemical preparation of polythiophene via 2,5-bis(trimethylsilyl)thiophene

Electrochemical polymerization of 2,5-bis(trimethylsilyl) thiophene produced highly conducting films which showed infrared spectra, visible-near infrared absorption spectra, and cyclic voltammograms identical to films prepared from thiophene. Elemental analysis indicated that almost all silicon atoms were eliminated during the electrochemical polymerization. However, scanning electron microscopy showed a morphological difference between the films from 2,5-bis(trimethylsilyl)thiophene and from thiophene. The electrochemical polymerization of bis(2-thienyl)dimethylsilane, 1,2-bis(2-thienyl)tetramethyldisilane, and bis(2-thienyl)diphenylsilane also produced polythiophene films having unique morphologies quite different from the conventional ones. These findings indicate that these electrochemical procedures must be useful for preparation of new conjugated polymers. © 1992 John Wiley & Sons, Inc.     

Stereoselective Synthesis and Diels-Alder Reactions of (Z)- and (E)-1,2-bis(Phenylthio)-1,3-Butadiene

Bromination of 3-phenylthio-2-sulfolene (2) with N-bromosuccinimide gave 2-bromo-3-phenylthio-2-sulfolene (3) which was converted mainly to 2,3-bis(phenylthio)-2-sulfolene (4) by treatment with sodium phenylthiolate. Thermal desulfonylation of 4 at different temperatures in the presence of a base (DBU) yielded stereoselectively the (Z)- and (E)-1,2-bis(phenylthio)-1,3-butadiene (6). These two geometric isomers could be thermally interconverted. The Diels-Alder reactions of 6 were also investigated. Only the (Z)-diene 6a could undergo the Diels-Alder reaction; the (E)-diene 6b was in situ converted to the Z isomer before undergoing (he Diels-Alder reaction. The reaction of 6a with N-phenylmaleimide gave the cycloaddition product 7 with complete endo selectivity, but under daylight or during chromatography it readily underwent a thioallylic rearrangement to yield 8 with inversion of configuration. The cycloaddition of 6a with methyl acrylate proceeded regiospecifically, but generating a mixture of endo and exo isomers. The endo/exo ratio could be increased by using ZnCl₂ as the catalyst.     

Synthesis, characterization, and C-H activation reactions of novel organometallic O-donor ligated Rh(III) complexes

The synthesis and characterization of the O-donor ligated, air and water stable organometallic complexes trans- (2), and cis-(hfac-O,O)₂Rh(CH₃)(py) (3), trans-(hfac-O,O)₂Rh(C₆H₅)(py) (4), cis-(hfac-O,O)₂Rh(C₆H₅)(py) (5), and cis-(hfac-O,O)₂Rh(Mes)(py) (6) (where hfac-O,O = κ²-O,O-1,1,1,5,5,5-hexafluoroacetylacetonato) are reported. These compounds are analogues to the O-donor iridium complexes that are active catalysts for the hydroarylation and C-H activation reactions as well as the bis-acetylacetonato rhodium complexes, which we recently reported. The trans-complex 2 undergoes a quantitative trans to cis isomerization in cyclohexane to form 3, which activates C-H bonds in both benzene and mesitylene to form compounds 5 and 6, respectively. All of these compounds are air and water stable and do not lead to decomposition products. Complex 5 promotes hydroarylation of styrene by benzene to generate dihydrostilbene.     

Synthesis of fused N-heterocycles via tandem C-H activation

The synthesis of fused N-heterocycles has been developed using an intramolecular cyclisation of purines or benzimidazoles. A range of medium and large rings were prepared.     

Synthesis and characterization of diiron(I) 1,2-dimethylethanedithiolate complexes with bridging or chelating 1,2-bis(diphenylphosphino)ethylene

The reaction of complex [μ-SCH(CH₃)CH(CH₃)S-μ]Fe₂(CO)₆ (1) with trans-1,2-bis(diphenylphosphino)ethylene (trans-dppv) in the presence of Me₃NO?2H₂O in CH₂Cl₂/CH₃CN afforded complex {[μ-SCH(CH₃)CH(CH₃)S-μ]Fe₂(CO)₅}₂(trans-dppv) (2) with a bridging dppv. Complex [μ-SCH(CH₃)CH(CH₃)S-μ]Fe₂(CO)₄(cis-dppv) (3) was prepared by the reaction of 1 with cis-dppv and Me₃NO?2H₂O. The new complexes 2 and 3 were characterized by elemental analysis, spectroscopy, and X-ray diffraction analysis.     

Synthesis of unsymmetrical 1,2-bis(diorganochlorosilyl)ethanes

Unsymmetrical 1,2-bis(diorganylsilyl)ethanes were synthesized by two procedures. Hydrosilylation of chloro(vinyl)silanes were used to obtain compounds of the general formula ClMe₂SiCH₂CH₂SiRMeCl with different substituents (R = Et, Vin, Ph) on the silicon atom. Chlorodealkylation of 1,2-bis(trialkylsilyl)ethanes gave compounds of the general formula ClAlk₂SiCH₂CH₂SiAlk₂Cl (Alk = Me, Et, Pr). It is established that the latter reaction provides high yields only with Me-and Et-substituted compounds, whereas Pr-substituted products are formed in poor yields. The mechamism of this reaction based on quantum-chemical calculations is offered.