Dancing of palladacycles around a "juggler" 2,2-diacetyl-1,1-ethylenedithiolato ligand in a trinuclear Pd(II) complex

A trinuclear Pd complex containing a mu3-1,1-ethylenedithiolato ligand has been synthesized and its structure confirmed by X-ray crystallography. It is the first example of a 1,1-ethylenedithiolato complex containing an anionic carbon sigma donor. This compound shows an unprecedented fluxional behavior in solution, by which the three palladacycles exchange around the dithiolene. The activation parameters for this process have been derived by NMR line shape analysis, and a mechanism is proposed.     

Synthesis of N-vinyl 2,2-bisphosphonoaziridines from 1,1-bisphosphono-2-aza-1,3-dienes

N-Vinyl 2,2-bisphosphonoaziridines are formed by treatment of 1,1-bisphosphono-2-aza-1,3-dienes with diazomethane. Depending on the substituents at the 4-position of the 1,1-bisphosphono-2-aza-1,3-dienes, exclusively 1-(ethenylamino)-2-phosphonoethenylphosphonates or mixtures of 1-(ethenylamino)-2-phosphonoethenylphosphonates and 2-imino-2-phosphonoethylphosphonates are obtained as side products.     

Access to "Friedel-Crafts-restricted" tert-alkyl aromatics by activation/methylation of tertiary benzylic alcohols

Herein we describe a two-step protocol to prepare m-tert-alkylbenzenes. The appropriate tertiary benzylic alcohols are activated with SOCl(2) or concentrated HCl and then treated with trimethylaluminum, affording the desired products in 68-97% yields (22 examples). This reaction sequence is successful in the presence of a variety of functional groups, including acid-sensitive and Lewis-basic groups. In addition to t-Bu groups, 1,1-dimethylpropyl and 1-ethyl-1-methylpropyl groups can also be installed using this method.     

利用“Click”反应制备含有(R)-(+)-BINOL的有机聚合物及其钛配合物在不对称加成反应中的催化性能

以自制的(R)-(+)-1,1’-联二萘酚[(R)-(+)-BINOL]的衍生物(R)-(+)-6,6’-二乙炔-1,1’-联二萘酚和1,4-对苯二叠氮为原料,经由"Click"反应(Huisgen 1,3-偶极环加成反应)制备出含有(R)-(+)-BINOL的有机聚合物(Polymer),利用傅里叶变换红外光谱仪(FTIR)、粉末X射线衍射仪(XRD)和扫描电子显微镜(SEM)对Polymer的组成、结构和形貌进行了表征.Polymer经过与Ti(OiPr)4配位合成出一种新型的非均相手性金属催化剂(Polymer-Ti),该催化剂在催化二乙基锌和多种芳香醛的不对称加成反应中都表现出非常高的芳香醛转化率和较好的对映体选择性,而且可以在二乙基锌和苯甲醛的不对称加成反应中循环使用.     

Enantioselective direct aldol reaction "on water" promoted by chiral organic catalysts

[structure: see text]. 1,1'-Binaphthyl-2,2'-diamine-based (S)-prolinamides in the presence of stearic acid were able to promote the direct aldol condensation of cyclohexanone and other ketones with different aldehydes in the presence of a massive amount of water in very good yields, high diastereoselectivity, and up to 99% ee. The behavior of both C2- and C1-symmetric catalysts in combination with different additives was investigated, and a preliminary experiment of recovering and recycling of the catalytic system was also attempted.     

Mass-spectrometric fragmentation of <Emphasis Type="Italic">N,N</Emphasis>-dimethyl-4-methoxy-6-polynitromethyl-1,3,5-triazin-2-amines

Mass-spectrometric fragmentation of N,N-dimethyl-4-methoxy-6-X-1,3,5-triazin-2-amine (X = fluorodinitromethyl, chlorodinitromethyl, bromodinitromethyl, trinitromethyl, 1,1-dinitroethyl, 2-hydroxy-1,1-dinitroethyl) under electron impact was studied. The stability of the molecular ion and the main fragmentation pathways are discussed.     

Synthesis and cytotoxic activity of derivatives of the <Emphasis Type="Italic">tert</Emphasis>-butyl ester of 7<Emphasis Type="Italic">Z</Emphasis>-acetylmethylene-3-methyl-3-cephem-4-carboxylic acid

The condensation of the acetylmethylene group in the tert-butyl esters of 7Z-acetylmethylene-3-methyl-3-cephem-4-carboxylic acid and 7Z-acetylmethylene-3-methyl-1,1-dioxo-3-cephem-4-carboxylic acid and in 7Z-acetylmethylene-3-methylene-1,1-dioxo-3-cephem with arylmethoxyamines and O-alkylation of the tert-butyl ester of 7Z-(2-hydroxyimino)propylidene-3-methyl-1,1-dioxo-3-cephem-4-carboxylic acid using substituted benzyl bromides as well as pyridylmethyl chlorides gave arylmethoxyimino and pyridylmethoxyimino derivatives of these compounds in the syn and anti isomeric forms. The Vilsmaier reagent was used to introduce the N,N-dimethylaminomethylene group at C-2 of the cephem system in the tert-butyl esters of 7Z-[2-(arylmethoxyimino)propylidene]-3-methyl-1,1-dioxo-3-cephem-4-carboxylic acid. Subsequent transformation of the N,N-dimethylaminomethylene cephems using hydroxylamine led to 3Z-[2-(anti-arylmethoxyimino)propylidene]-tert-butoxycarbonylmethyl-4-(5-methyl-4-isoxazolylsulfonyl)- azetidin-2-ones. Condensation of the acetyl group in the tert-butyl ester of 7Z-acetylmethylene- 3-methyl-1,1-dioxo-3-cephem-4-carboxylic acid with 4-bromophenylhydrazine gave a cephem with a 2-(4-bromophenylhydrazono)propylidene group at C-7. Acylation of the tert-butyl ester of 7Z-(2-hydroxyimino)propylidene-3-methyl-1,1-dioxo-3-cephem-4-carboxylic acid by 2-bromobenzoyl chloride gave a cephem with a 2-(2-bromo-benzoyloxyimino)propylidene group at C-7. Biological screening of these products towards to malignant and normal cells in vitro showed that their antitumor activity and cytotoxic selectivity towards to malignant and normal cells depend on the structure and configuration of the arylmethoxyimino and pyridylmethoxyimino groups in the 7-alkylidene substituent as well as on the presence or absence of N,N-dimethylaminomethylene and carboxyl groups, respectively, at C-2 and C-4 of the cephem system.     

Synthesis and optical properties of (<Emphasis Type="Italic">S</Emphasis>)-Nobin

A preparative method of synthesis of optically pure S-2-amino-2′-hydroxy-1,1′-binaphthyl (S-Nobin), the precoursor in the synthesis of other asymmetric 1,1-binaphthyls applied as the ligands at the creation of the catalysts of asymmetric synthesis, is modified. The UV and CD spectra of this compound were studied in detail and essential dependence of spectral information on the solvent nature was shown.     

Production of "internal surface reversed-phase" supports: the hydrolysis of selected substrates from silica using chymotrypsin

The degree of hydrolysis of substrates attached to silica supports with alpha-chymotrypsin has been evaluated relative to the production of "internal surface reversed-phase" supports. The peptide substrates N-tert.-butoxycarbonyl-L-phenylalanine (Boc-L-Phe), N-carbobenzoxy-L-valine-L-phenylalanine, N-acetyl-L-phenylalanine (acetyl-L-Phe) and N-benzoyl-L-phenylalanine as well as phenylpropionic acid were attached to glycerylpropyl-bonded silica via a diamine spacer using 1,1-ethyl-3-(3-dimethylaminopropyl) carbodiimide as a coupling catalyst. The products released from the silica support on enzyme treatment were quantified by high-performance liquid chromatography. Boc-L-Phe and acetyl-L-Phe were successfully cleaved from the rigid silica matrix in high yields, whereas the remaining substrates were hydrolyzed to a lesser extent.     

Synthesis of spiro[5.4]decenones and their transformation into bicyclo[4.4]deca-1,4-dien-3-ones by domino "elimination- double-Wagner-Meerwein-rearrangement" reactions

The [3+3] cyclization of 1,3-bis-silyl enol ethers with 1,1-diacylcyclopentanes allows a convenient synthesis of spiro[5.4]decenones. Treatment of these compounds with trifluoroacetic acid (TFA) afforded a great variety of bicyclo[4.4.0]deca-1,4-dien-3-ones containing an angular alkyl group. This core structure occurs in a number of pharmacologically relevant natural products.     

Studies on indolic mould metabolites. Total synthesis of l-prolyl-2-methyltryptophan anhydride and deoxybrevianamide e

Syntheses of l - prolyl - 2 - methyl - l - tryptophan anhydride, l -prolyl - 2 - methyl - d - tryptophan anhydride, deoxybrevianamide E, and l - prolyl - 2 - (1,1 - dimethylallyl) - d- tryptophan anhydride are described. A route for the conversion of deoxybrevianamide E into brevianamide E has also been examined.     

Unexpected transformation of 1,1"-methylenebis(2-naphthol) into 1,2,1",2"-tetrahydrospiro(naphthalene-1,3"-naphtho[2,1-b]pyran)-2-one, a spirodimer of 1,2-naphthoquinone 1-methide, in the presence of boric acid and paraformaldehyde

When heated in benzene with paraformaldehyde and boric acid, 1,1"-methylenebis(2-naphthol) easily decomposes to 1,2-naphthoquinone 1-methide, which dimerizes into a spirodimer. The by-product of the reaction is 14Í-dibenzo[a,j]xanthene.     

Synthesis and structures of 1,1"-dialkyl-3,3"-bidiaziridines

First representatives of 3,3"-bidiaziridines, viz., 1,1"-dialkyl-3,3"-bidiaziridines, were synthesized and isolated as mixtures of two diastereomers. In the case of Alk = Me, the diastereomers were separated. It was demonstrated by nuclear Overhauser effect experiments and X-ray diffraction analysis that the diastereomers are the racemate (rac-1R*,2R*,3S*,1"R*,2"R*,3"S*) and the meso-form (1S*,2S*,3R*,1"R*,2"R*,3"S*).     

Synthesis of carbosilane block copolymers by means of a living anionic polymerization of 1,1-diethylsilacyclobutane

Block polymerization of 1,1-diethylsilacyclobutane with styrene derivatives and methacrylate derivatives was investigated. Sequential addition of styrene to a living poly(1,1-diethylsilabutane), which was prepared from phenyllithium and 1,1-diethylsilacyclobutane in THF–hexane at −48°C, gave poly(1,1-diethylsilabutane)-b-polystyrene. Similarly, addition of 4-(tert-butyldimethylsiloxy)styrene to the living poly(1,1-diethylsilabutane) provided poly(1,1-diethylsilabutane)-b-poly(4-(tert-butyldimethylsiloxy)styrene). Poly(1,1-diethylsilabutane)-b-poly(methyl methacrylate) was obtained by treatment of living poly(1,1-diethylsilabutane) with 1,1-diphenylethylene followed by an addition of methyl methacrylate. Poly(1,1-diethylsilabutane)-b-poly(2-(tert-butyldimethylsiloxy)ethyl methacrylate) was also synthesized by adding 2-(tert-butyldimethylsiloxy)ethyl methacrylate to the living poly(1,1-diethylsilabutane) which was end-capped with 1,1-diphenylethylene in the presence of lithium chloride. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2699–2706, 1998     

SP-PLP-EPR study of chain-length-dependent termination in free-radical polymerization of n-dodecyl methacrylate, cyclohexyl methacrylate, and benzyl methacrylate: evidence of "composite" behavior

The chain-length dependence of the termination rate coefficient in n-dodecyl methacrylate (DMA), cyclohexyl methacrylate (CHMA), and benzyl methacrylate (BzMA) bulk free-radical homopolymerizations at ambient pressure and at temperatures from -20 to 0 degrees C is deduced using the recently developed technique of SP-PLP-EPR: pulsed-laser polymerization (PLP) in which time-resolved EPR measurement of radical concentration, cR, is made following each single pulse (SP) of an excimer laser. The decay of cR results from termination of radicals of almost identical size. Their chain length, i, increases linearly with time, t, after applying a SP. The rate coefficient, kt(i,i), for termination of two radicals of size i is determined by fitting the experimental cR vs t data. This process demonstrates that (at least) two power-law exponents are necessary to describe kt(i,i) over the extended chain-length range of i = 1 to 1000. This is consistent with the so-called "composite model" , which uses power-law exponents alpha(S) and alpha(L) to describe termination of radicals either shorter or longer, respectively, than a crossover chain length, ic. The fourth parameter obtained from fitting the SP-PLP-EPR data with this model is kt(1,1), the termination rate coefficient for two radicals of degree of polymerization 1. Previous DMA experiments are reanalyzed while new experimental results are reported and analyzed for CHMA and BzMA. The parameter values for CHMA and BzMA termination at 0 degrees C are almost identical-kt(1,1) approximately 3 x 10(7) L mol(-1) s(-1), alpha(S) approximately 0.50, ic approximately 90, and alpha(L) approximately 0.21-and they are close to those for DMA at 0 degrees C: kt(1,1) approximately 1 x 10(7) L mol(-1) s(-1), alpha(S) approximately 0.64, ic approximately 50, and alpha(L) approximately 0.18. The results fully support the composite model in that the chain-length dependence is more pronounced for shorter than for longer radicals, i.e., alpha(S) > alpha(L). Moreover, the power-law exponent that characterizes termination of long-chain radicals is close to the theoretical value of alpha(L) = 0.16. In fact all parameter values-including the small differences between DMA and CHMA/BzMA-are more-or-less in accord with expectations based on polymer dynamics. Furthermore, our results suggest that termination of methacrylate radicals with large cyclic or long n-alkyl substituents may be affected by steric shielding of the radical functionality.     

Synthetic utility of 3-(perfluoro-1,1-dimethylbutyl)prop-1-ene. Part VI. A free-radical addition of CCl4 and CBr4 and dehydrohalogenation of the adducts

Heating the title compound 1 in excess CCl₄ and in the presence of a free-radical initiator (t-butyl peroxide) at 120 °C afforded 1,1,1,3-tetrachloro-4-(perfluoro-1,1-dimethylbutyl)butane (2) as the main product together with considerable amounts of cyclic dimer, 1,4-bis(perfluoro-1,1-dimethylbutyl)cyclohexane (3). Reaction of 1 with CBr₄ at 120 °C gave 1,1,1,3-tetrabromo-4-(perfluoro-1,1-dimethylbutyl)butane (4) as the sole product while at 220 °C a mixture of 1,2-dibromo-3-(perfluoro-1,1-dimethylbutyl)propane (5) and 1,1-dibromo-4-(perfluoro-1,1-dimethylbutyl)buta-1,3-diene (6) was formed. Treatment of adducts 2 and 4 with methanolic potassium hydroxide at ambient temperature gave mixtures of 1,1,3-trihalo-4-(perfluoro-1,1-dimethylbutyl)but-1-enes (7) or (8) and 1,1-dihalo-4-(perfluoro-1,1-dimethylbutyl)buta-1,3-dienes (9) or (6) in ratios depending on the adduct to base ratio and on the reaction conditions. Using an excess of the base and reflux temperature, adduct 4 and diene 6 were converted into methyl 4-(perfluoro-1,1-dimethylbutyl)buten-3-oate (10).     

Reaction of <Emphasis Type="Italic">N</Emphasis>-methyl-<Emphasis Type="Italic">N,N</Emphasis>-bis(silatranylmethyl)amine with trichlorosilane

N,N-Bis(silatranylmethyl)methylamine reacts with trichlorosilane to form the amine hydrochloride and perchloropolysilane, the product of polymerization of dichlorosilylene. In the presence of 1,3-butadiene the main products of the reaction are the amine hydrochloride and 1,1-dichlorosilacyclopentene-3, the product of 1,4-addition of dichlorosilylene to 1,3-butadiene.     

Embedding an allylmetal dimer in a chiral cavity: the unprecedented stereoselectivity of a twofold wittig [1,2]-rearrangement

After alpha,alpha'-dimetalation, both 2,2'-diallyloxy-1,1'-binaphthyl and 2,2'-di-2-methylallyloxy-1,1'-binaphthyl undergo the Wittig rearrangement with perfect diastereoselectivity. When racemic 1,1'-binaphthyl-2,2'-diol ("BINOL") is used as the starting material, it gives rise to a 1:1 mixture of antipodal stereoisomers, whereas enantiomerically pure (M)-2,2'-diallyloxy-1,1'-binaphthyl affords (M)-(S,S)-1,1-(1,1'-binaphthyl-2,2'-diyl)bis(2-propen-1-ol) as the sole product. The (M)-(S,S)/(P)-(R,R) mixture resulting from the rearrangement of racemic 2,2'-diallyloxy-1,1'-binaphthyl can be effectively subjected to a kinetic racemate resolution by applying the Sharpless-Katsuki asymmetric epoxidation. The single-sided Wittig rearrangement of 2-allyloxy-2'-propyloxy-1,1'-binaphthyl proceeds without any diastereoselectivity as this substrate can only be monometalated and hence is incapable of intramolecular aggregate formation which is instrumental for the observed stereoselectivity.     

Reaction of gem-dibromocyclopropanes with diphenylphosphide ion

Diphenylphosphide ion undergoes a photostimulated reaction with 7,7-dibromobicyclo[4.1.0]heptane and 1,1-dibromo-2,2,3,3-tetramethylcyclopropane involving both ionic and radical steps to afford cyclopropyldiphenylphosphines resulting from substitution and reduction.     

2-叠氮基-1,1-二硝基乙基取代苯衍生物的合成

详细研究了2-叠氮基-1,1-二硝基乙基取代苯衍生物的合成方法。由苯基二硝基甲烷钾盐经羟甲基化，磺酰酯化和叠氮化得到目标化合物：3-硝基-(2-叠氮基-1,1-二硝基乙基)苯(4b)，4-硝基-(2-叠氮基-1,1-二硝基乙基)苯(4c)，m-二(2-叠氮基-1,1-二硝基乙基)苯(10)和p-二(2-叠氮基-1,1-二硝基乙基)苯(15)。