Convenient synthesis of β,γ-unsaturated γ-dithiolactones from allenylsilver(I) compounds

Allenylsilver(I) compounds react with carbon disulfide to silver(I) 3-alkynedithioates; β,γ-unsaturated γ-dithiolactones are formed by spontaneous cyclisation of these dithioates.     

Palladium(O)-promoted synthesis of functionally substituted allenes by means of organozinc compounds

The paper describes new routes to aryl-, vinyl-, and 1-alkynylallenes and to diallenes $\text{via}$ Pd(PPh₃)₄-promoted reaction of propargylic or allenic halides with appropriate organozinc halides. Propargylic acetates are also suited to prepare such allenes.     

A simple synthetic route to substituted cyclopentenolones

Preparation of novel cyclopent-3-ene-1,2-dione dimers from γ-substituted crotonate esters and dimethyl oxalate by vinylogous double Claisen condensations has given access to a series of polyfunctional cyclopentane derivatives potentially useful in synthesis.     

Convenient synthesis of (triphenyl)germyl and (triphenydstannyl substituted allenes

Allenyl-germanes and -stannanes, Ph₃MC(R)CCR′R″ (M = Ge, Sn) can be obtained, generally in excellent yield, through alkylcopper(I)-induced 1,3-substitution of the propargylic chlorides Ph₃MCCCR′R″Cl. In the tin series, however transmetallation is the main process when MeCu, H₂CCHCu or PhCu are used. The allenyl compounds in which R is (trimethylsilyl)ethynyl or 4,4-dimethyl-1,2-pentadienyl can be obtained by using the organozinc compounds instead of the copper(I) compound and using tetrakis(triphenylphosphine)palladium as catalyst.     

Heterocycles. Part I. A new route to the synthesis of substituted 2-aminopyrimidines

Heterocyclic aldehydes (A) reacted with alkyl aryl ketones (B) to give the corresponding 1,3-diaryl-2-propen-1-ones (Ia-1). Condensation of these chalcones with guanidine produced the corresponding 2-amino-4,6-diarylpyrimidines (IIa-1). The structure of all products was substantiated by chemical and spectroscopic methods.     

1,2,3-triazole bound Au(I) (TA-Au) as chemoselective catalysts in promoting asymmetric synthesis of substituted allenes

The triazole-Au (TA-Au) complexes were identified as effective chemoselective catalysts in promoting propargyl ester/ether 3,3-rearrangements. The highly reactive allenes, which could not be isolated by simple cationic gold catalysts, were prepared in excellent yields (1% catalyst loading, >90% yields). Unlike other reported Au catalysts, the TA-Au provided effective chirality transfer without racemization over a long period of time, giving enantioenriched allenes with excellent stereoselectivity (1% catalyst loading, up to 99% ee).     

Metal catalysis in organic reactions. 17. A nickel-promoted route to substituted allenes by reaction of 1-bromo-1,2-dienes with alkyl metals.

Nickel complexes are found to be catalytically active in the cross-coupling reactions of allenic bromides with alkyl metals to give substituted allenes in excellent yields. The catalytic process proceeds generally with inversion of configuration in the allenyl moiety.     

Organosilicon compounds I. A novel synthesis of organosilicon substituted furfurals

The use of the diethylacetal moiety of 2-furfuraldiethylacetal as a carbonyl blocking agent during n-butyllithium metalations is described. The synthesis of 5-silicon substituted furfurals is accomplished for the first time with NMR data being employed as a means of structure proof. Furthermore, the isolation of the uniquely stable organo-lithium salt, 5-lithio-2-furfuraldiethylacetal, is reported.     

Silanes in organic syuthesis. 11. Regiocontrolled synthesis of α-hydroxymethylated (trimethylsilyl)allenes

The organometallic produced by reaction of trimethylsilylpropargyl bromide with aluminum amalgam in anhydrous tetrahydrofuran condenses readily with aldehydes and ketones to give allenic alcohols resulting from coupling α to the trimethylsilyl substituent.     

Organometallic compounds in organic synthesis: reactions of some tricarbonylcyclohexadienyliumiron complexes with 1,2-bis(trimethylsiloxy)-1-cyclopentene. A novel route to 2-(substituted)-2-cyclopenten-1-ones.

1,2-Bis(trimethylsiloxy)-1-cyclopentene reacts with a range of tricarbonylcyclohexadienyliumiron cations to give initially siloxy acyloins, treatment of which with MeOH-HCl gives the 2-(substituted)-2-cyclopenten-1-one in good yields (56–78%).     

Palladium(0)-promoted cross-coupling of allenylmetal compounds with aryl and vinyl iodides. A novel route to aryl- and vinyl-substituted allenes

The reaction of allenylmetal compounds, RR{′}CCCHM (I), with aryl and vinyl iodides, R I, have been studied. With Pd(PPh₃)₄ as catalyst a highly regioselective formation of allenes, RR{′}CC CHR″ (II), has been observed for MgCl, Cu, Cu_1/2,Li_1/2, Ag, Ag_1/2Li_1/2, or ZnCl, but not Li. The reaction of the iodides proceeds with retention of configuration.     

A simple synthesis route and characterisation of Co(3)Mo(3)C

A simple, one-step thermal decomposition method for the preparation of Co(3)Mo(3)C is reported in this paper. In this novel synthesis route, a mixed-salt precursor, containing Co(CH(3)COO)(2) x 4H(2)O, (HMT)(2)(NH(4))(4)Mo(7)O(24) x 2H(2)O (HMT = hexamethylenetetramine), and excess HMT is directly decomposed to the bimetallic carbide under flowing argon at 1023 K. The role of HMT in the preparation process has been investigated and a detailed reaction mechanism is proposed based on the experimental results. The bimetallic carbide is characterised by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, BET surface area measurement and X-ray photoelectron spectroscopy. Furthermore, the activity of the as-prepared Co(3)Mo(3)C is evaluated by a 3-methylpyridine hydrodenitrogenation (HDN) reaction. The catalyst produced from this method provides better reactivity compared to the Co(3)Mo(3)C catalyst prepared by the conventional temperature-programmed reduction method.     

A simple route to 3-(dihalomethylene)cyclo-alkenes

Thermolysis of a number of bicyclic trihalocyclopropanes (1; X, Y = halogen) in the presence of quinoline leads either to 3-(dihalomethylene)cyclo-alkenes (8,9,10) with loss of halogen X $\text{or}$ to ring expanded 1,2-dihalocycloalka-1,3-dienes (11,13) with loss of halogen Y, depending on ring size and on the nature of the halogen.     

Aminohaloborane in organic synthesis. VI. A simple enantioselective aldol synthesis

A simple asymmetric aldol condensation of acetophenone and benzaldehydes was performed via chiral vinylaminodichloroborane. The enatioselectivity was compared with that by a similar method using magnesium and lithium.     

Functionally substituted organotin compounds I. Addition of thiols to alkenyltin compounds

3-(Trialkylstannyl)propyl aryl sulphides (R₃SnCH₂CH₂CH₂SR′; R = Me, Et, Bu; R′ = Ph, p-tolyl) were prepared by the addition of arenethiols to allyltrialkyltin compounds. Preferential cleavage of the allyl group by the reaction R₃SnCH₂CHCH₂+R′SH→R₃SnSR′+CH₃CHCH₂ occurred when R = R′ = Bu and R = R′ = Ph. Diallyltin dibromide and benzenethiol gave stannous bromide. Mössbauer parameters of the products are recorded.