Preparation and oxidative coupling of bis[o-(hydrosilyl)phenyl]cuprates and bis[o-(fluorosilyl)phenyl]cuprates

Bis[o-(hydrosilyl)phenyl]cuprates and bis[o-(fluorosilyl)phenyl]cuprates were prepared by reacting [o-(hydrosilyl)phenyl]lithiums and [o-(fluorosilyl)phenyl]lithiums, respectively, with copper salts, such as CuCN and Cu(OPiv)₂. The phenylcuprates underwent oxidative coupling to afford 2,2′-bis(hydrosilyl)biphenyls and 2,2′-bis(fluorosilyl)biphenyls.     

Regioselective electrophilic cyclization of o-ethynylbenzyl phenyl selenides to (Z)-1-methylidene-2-phenyl-1,3-dihydro-1H-benzo[c]selenophenium salts

o-Ethynylbenzyl phenyl selenides regioselectively reacted with trifluoromethanesulfonic acid to afford the (Z)-1-methylidene-2-phenyl-1,3-dihydro-1H-benzo[c]selenophenium salts as the major products during the 5-exo-dig mode cyclization in good yields together with minor E isomers. The structure of the major (Z)-selenophenium salt was established by the single crystal X-ray crystallographic analysis using a tert-butyl derivative.     

Conjugate addition of amines to chiral 3-aziridin-2-yl-acrylates

Conjugate addition of benzylamine to chiral methyl cis-3-aziridin-2-yl-acrylates was successfully proceeded to yield 3-aziridin-2-yl-3-benzylaminopropionates in high yield with high stereoselectivity. The addition products were used for the asymmetric synthesis of vicinal diamine derivatives including 4-amino-5-methylpyrrolidin-2-one, 3,4-diaminopentanoate, and 5-chloromethyl-4-alkoxycarbonylmethylimidazolidin-2-one.     

Electronic states of radical cations of all-trans oligo[methyl(phenyl)silane]

The electronic states of radical cations of oligo[methyl(phenyl)silane] (OMPSi⁺) with all trans form (n = 2-8, where n is number of monomer unit of OMPSi) have been investigated by means of density functional theory (DFT) calculation to shed light on the mechanism of hole-transport in oligosilanes with phenyl group in the side chain. For the shorter oligomers (n < 3), the hole (unpaired electron) was widely distributed equivalently in both the Si main and side chains (55% for the Si main chain and 45% for the side chain). The distribution of hole on the chains was largely changed as a function of chain lengths (n). Ratios of the hole distribution on the main and side chains became almost constant at n = 7-8: 70% of spin density was distributed on the Si-main chain and 30% on the side-chain, which is much different from that of oligo(dimethyl)silane (the spin density on the methyl side chain was less than 3% of spin density). From these results, it was concluded that the hole in OMPSi⁺ can transfer by the mechanism for both intermolecular and the intrachain hole-transfer processes.     

The synthesis and electronic absorption spectra of 3-phenyl-3(4-pyrrolidino-2-substituted phenyl)-3H-naphtho[2,1-b]pyrans: further exploration of the ortho substituent effect

Introduction of a substituent into a sterically demanding 2-position of a 3-(4-pyrrolidinophenyl) ring of a 3,3-diaryl-3H-naphtho[2,1-b]pyran results in the generation of an additional short wavelength absorption band leading to organic photochromes that appear as dull shades of orange and red.     

Steric consequence of the diastereoselective addition of chiral lithium 2-(1-dimethylaminoethyl)phenyl cuprates to some enones

Conjugate addition of the mixed chiral species lithium [(S)-2-(1-dimethylaminoethyl)phenyl](2-thienyl)cuprate to (E)-4-phenyl-3-buten-2-one, 2-cyclohexenone or to 2-cyclopentenone proceeds with high diastereoselectivity. The first two enones gave crystalline adducts directly, while the non-crystalline cyclopentenone adduct was converted into a crystalline methiodide. The crystal structures of the compounds have been determined from single-crystal X-ray diffractometer data in order to reveal the configurations at the new chiral centres. In all three cases the configuration at the new asymmetric centre is S. (S,S)-4-[2-(1-Dimethylaminoethyl)phenyl]-4-phenyl-2-butenone, C₂₀H₂₅NO, crystallizes in space group P2₁ with a 7.604(2), b 9.398(5), c 12.290(6) Å, β 92.30(3)° and Z = 2. Full-matrix least-squares refinement of 273 structural parameters gave R = 0.066 for 1015 observed independent reflections. (S,S)-3-[2-(1-Dimethylaminoethyl)phenyl]-2-cyclohexanone, C₁₆H₂₃NO crystallizes in space group P2₁2₁2₁ with a 12.499(4), b 6.645(3), c 17.568(7) Å and Z = 4. Full-matrix least-squares refinement of 142 structural parameters gave R = 0.068 for 1507 observed independent reflections. (S,S)-1-[2-(3-Oxocyclopentyl)phenyl]ethyltrimethylammonium iodide, C₁₆H₂₄NOI, crystallizes in space group P4₁, with a 10.569(3), c 30.895(7) Å and Z = 8; there are thus two crystallographically independent cations in the asymmetric unit. Full-matrix least-squares refinement of 342 structural parameters gave R = 0.054 for 2119 observed independent reflections.The (S,S)-configuration observed in these adducts indicates that the conjugate addition gives the least crowded lithium enolate as the major product.     

Synthesis and some transformations of methyl [4-(oxoacetyl)phenyl]carbamate

The oxidation of methyl (4-acetylphenyl)carbamate with selenium dioxide in dioxane–water (30: 1) gave methyl [4-(oxoacetyl)phenyl]carbamate whose condensation with ethyl acetoacetate or diethyl malonate and hydrazine hydrate afforded ethyl 3-methyl-6-[4-(methoxycarbonylamino)phenyl]pyridazine-4-carboxylate and methyl {4-[5-(hydrazinecarbonyl)-6-oxo-1,6-dihydropyridazin-3-yl]phenyl}carbamate, respectively. The reaction of methyl [4-(oxoacetyl)phenyl]carbamate with o-phenylenediamine in dimethylformamide–ethanol on heating led to the formation of methyl [4-(quinoxalin-2-yl)phenyl]carbamate. Methyl {4-(5,7-dioxo- 4,4a,5,6,7,8-hexahydropyrimido[4,5-c]pyridazin-3-yl)phenyl}carbamate and methyl {4-(5-oxo-7-sulfanylidene- 4,4a,5,6,7,8-hexahydropyrimido[4,5-c]pyridazin-3-yl)phenyl}carbamate were synthesized by reactions of methyl [4-(oxoacetyl)phenyl]carbamate with barbituric and thiobarbituric acids, respectively, and hydrazine hydrate in the presence of zirconyl chloride octahydrate at room temperature.     

An efficient chiral synthesis of (R)-N-[3-acetyl-4-(2-hydroxy-3-isopropylamino-propoxy)phenyl]-butanamide with high enantioselectivity

R-Enantiomer of the β-receptor antagonist N-[3-acetyl-4-(2-hydroxy-3-isopropylamino-propoxy)phenyl] butanamide with high enantioselectivity was synthesized from cheap starting materials and enantiopure chiral reagent through an efficient, convenient and practical synthetic strategy. Title product was detected by ¹H NMR, ¹³C NMR, and MS, and the enatiomeric excess was determined by chiral HPLC analysis using a chiracel AD-H column. Supported by the National Natural Science Foundation of China (Grant Nos. 20472090 & 10576034) and PLA General Armament Department (Grant No. 9140A28010707zk7301)     

Base cleavage of substituted [phenyl(2-thienyl)methyl]- and [phenyl(2-furyl)methyl]-trimethylsilane. Stabilization of carbanionic centres by 2-thienyl and 2-furyl groups

Rates of cleavage by NaOMEMeOH at 25°C have been determined for (2-thienyl)₂CHSiMe₃ and for the compounds Ph(2-thienyl)CHSiMe₃ and Ph(2-furyl)CHSiMe₃ and some of their derivatives with a substituent in the m- or p-position of the phenyl group or the 5-position of the heterocyclic group. The results indicate that the 2-thienyl and 2-furyl groups stabilize a carbanionic centre more effectively than a phenyl group, and the following approximate pK_a values can be derived: Ph₂CH₂, 33.4; Ph(2-thienyl)CH₂, 30.0; Ph(2-furyl)CH₂, 29.6; (2-thienyl)₂CH₂, 27.1. The effect of the 2-Cl substituent in the thiophen ring is close to that of the p-Cl substituent in the benzene ring, and the effects of the p-Me substituents on the benzene ring are very close to those of the 2-Me substituents on the thiophen or furan rings. The product and rate isotope effects (determined by use of MeOD) are consistent with separation of the carbanion in the rate-determining step.     

Preparation, crystal structure, and spectroscopic, chemical, and electrochemical properties of (2E,4E)-4-[4-(dimethylamino)phenyl]-1-(3-guaiazulenyl)-1,3-butadiene compared with those of (E)-2-[4-(dimethylamino)phenyl]-1-(3-guaiazulenyl)ethylene

Wittig reaction of 3-[4-(dimethylamino)phenyl]propanal (5) with (3-guaiazulenylmethyl)triphenylphosphonium bromide (4) in ethanol containing NaOEt at 25 °C for 24 h under argon gives the title (2E,4E)-1,3-butadiene derivative 6E in 19% isolated yield. Spectroscopic properties, crystal structure, and electrochemical behavior of the obtained new extended π-electron system 6E, compared with those of the previously reported (E)-2-[4-(dimethylamino)phenyl]-1-(3-guaiazulenyl)ethylene (12), are documented. Furthermore, reaction of 6E with 1,1,2,2-tetracyanoethylene (TCNE) in benzene at 25 °C for 24 h under argon affords a new Diels-Alder adduct 8 in 59% isolated yield. Along with spectroscopic properties of the [π4+π2] cycloaddition product 8, the crystal structure, possessing a cis-3,6-substituted 1,1,2,2-tetracyano-4-cyclohexene unit, is shown. Moreover, reaction of 6E with (E)-1,2-dicyanoethylene (DCNE) under the same reaction conditions as the above gives no product; however, this reaction in p-xylene at reflux temperature (138 °C) for four days under argon affords a new Diels-Alder adduct 9 in 54% isolated yield. Although reaction of 6E with DCNE in toluene at reflux temperature (110 °C) for four days under argon provides 9 very slightly, reaction of 6E with dimethyl acetylenedicarboxylate (DMAD) in toluene at reflux temperature for two days under argon yields a new Diels-Alder adduct 10, in 58% isolated yield, which upon oxidation with MnO₂ in CH₂Cl₂ at 25 °C for 1 h gives 11, converting a (CH₃)₂N-4″ into CH₃NH-4″ group, in 37% isolated yield. The crystal structure of 11 supports the molecular structure 10 possessing a partial structure cis-3,6-substituted 1,2-dimethoxycarbonyl-1,4-cyclohexadiene. The title basic studies on the above are reported in detail.     

Chlorosulfonic acid-mediated cyclization of 4-phenyl-3-isocoumarincarboxylic acids and 4-phenyl-3-isoquinolinonecarboxylic acids: an efficient synthesis of 3-oxoindeno[2,1-c]isocoumarins and 3-oxoindeno[2,1-c]isoquinolinones

A highly efficient and clean method has been developed for the synthesis of 3-oxoindeno[2,1-c]isocoumarins and 3-oxoindeno[2,1-c]isoquinolinones from 4-phenyl-3-isocoumarincarboxylic acids and 4-phenyl-3-isoquinolinonecarboxylic acids, respectively.     

An efficient chiral synthesis of (R)-N-[3-acetyl-4-(2-hydroxy-3-isopropylamino-propoxy)phenyl]-butanamide with high enantioselectivity

R-Enantiomer of the β-receptor antagonist N-[3-acetyl-4-(2-hydroxy-3-isopropylamino-propoxy)phenyl] butanamide with high enantioselectivity was synthesized from cheap starting materials and enantiopure chiral reagent through an efficient,convenient and practical synthetic strategy.Title product was detected by 1H NMR,13C NMR,and MS,and the enatiomeric excess was determined by chiral HPLC analysis using a chiracel AD-H column.     

Structure of 1-phenyl-3-[o-hydroxy (methoxy) phenyl]-5-benzazolylformazans

A number of benzazolylhydrazones and benzazolylformazans containing an o-hydroxy or o-methoxy group in the phenyl ring attached to the meso-carbon atom were synthesized. The structure of the compounds in various solvents was studied by means of IR and UV spectroscopy and by determination of the ionization constants. The participation of the o-hydroxy group in the formation of an intramolecular hydrogen bond was demonstrated. The interrelationship between the structure and color of the formazans was investigated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1498–1504, November, 1976.     

Is samoquasine A indeed benzo[f]phthalazin-4(3H)-one? Unambiguous, straightforward synthesis of benzo[f]phthalazin-4(3H)-one and its regioisomer benzo[f]phthalazin-1(2H)-one

In search for the structural elucidation of samoquasine A, a natural product isolated from the seeds of Annona squamosa L., two benzo[f]phthalazinone isomers have been synthesized. The synthetic pathway followed to build up these skeletons is based on the combination of two Suzuki reactions on a pyridazinone precursor and a ring closure reaction via a condensation reaction. ¹H NMR data of the synthesized compound allowed to establish that the structure of the natural product samoquasine A is not benzo[f]phthalazin-4(3H)-one, as previously suggested.