New routes to 1,1-dichloro-4-methyl-1,3-pentadiene (original) (raw)
Recent Advances in the Chemistry of Pentafulvenes
Chemical Reviews, 2017
Pentafulvenes are a unique class of compounds that originally attracted attention due to their propensity to display nonbenzenoid aromaticity. Subsequently, they were recognized as valuable synthons for the construction of a wide range of compounds by virtue of their ability to display multiple cycloaddition profiles. Naturally, this area of organic chemistry has experienced rapid growth over the last five decades, fueled by elegant work showcasing the unique reactivity of pentafulvenes in a plethora of cycloaddition reactions. In this Review, we have attempted to provide a systematic account of the methods for the generation of pentafulvenes, their rich and varied cycloaddition chemistry, organometallic reactions, and theoretical studies that support their versatility. Further, we have highlighted their applications in the synthesis of a variety of complex structural frameworks. It is our conviction that this Review will be useful to a wide range of chemists, and will spur further research in this promising area.
Journal of the American Chemical Society, 1996
The reactions of [Pd(C 6 F 5 )Br(CH 3 CN) 2 ] with 1,4-pentadiene or 3-methyl-1,4-pentadiene at low temperature afford, after insertion of one double bond into the Pd-C 6 F 5 bond, two types of η 1 -η 2 -pentenylpalladium derivatives: the 4.5-membered palladacycles [Pd 2 (µ-Br) 2 (5-Pf-3-R-1,2,4-η 1 -η 2 -pentenyl) 2 ] (Pf ) C 6 F 5 ; R ) H (2a), Me (2b)) and the 5.5-membered metallacycles [Pd 2 (µ-Br) 2 (5-Pf-3-R-1,2,5-η 1 -η 2 -pentenyl) 2 ] (R ) H (3a), Me (3b)). Both enyls isomerize to η 3 -allylic derivatives following two competitiVe pathways, i.e. (i) Pd migration or (ii) cyclopropane formation and reopening, which lead to the isomeric η 3 -allylpalladium complexes [Pd 2 (µ-Br) 2 (5-Pf-3-R-1-3-η 3pentenyl) 2 ] (R ) H (5a), Me (5b)) and [Pd 2 (µ-Br) 2 (4-Pf-3-(CH 2 R)-1-3-η 3 -butenyl) 2 ] (R ) H (6a), Me (6b)), respectively. After the cyclopropane formation-reopening process, [Pd 2 (µ-Br) 2 (3-CH 2 Pf-1,2,5-η 1 -η 2 -pentenyl) 2 ] (8) is also formed which isomerizes to 6b. The reaction of a mixture of the η 1 -η 2 -pentenyl complexes at low temperature with CO/NaOMe gives methyl ester derivatives. Again, the formation of the major ester CH 2 dCH(CH 2 Pf)-CHRCOOMe involves cyclopropane formation-reopening in the enyl derivative 2. An unusual acyl complex, [Pd-(µ-Br)(η 1 -η 2 -3-CH 2 Pf-1-oxo-4-pentenyl)] 2 (15) containing a chelating η 2 -η 1 -olefin acyl moiety has been characterized. + + Scheme 2 Scheme 3 7146
Gallium(III) Halide Promoted Synthesis of 1,3,5-Triaryl-1,5-dihalo-1,4-pentadienes
ChemInform, 2005
Aryl substituted alkynes undergo smooth coupling with aldehydes in the presence of gallium (III) halides under extremely mild conditions to afford the corresponding 1, 3, 5-triaryl-1, 5-dihalo-1, 4-pentadienes in good yields with E, Z-selectivity. Similarly 1, 3, 5-triaryl-1, 5-...
A convenient route to prepare isodicyclopentadiene—precursor of 1,5-dihydro-pentalene
Tetrahedron Letters, 2007
A new route to prepare tricyclo[5.2.1.0 2,6 ]deca-2,4-diene (isodicyclopentadiene) was developed. This new route passes through a brominated (5-bromotricyclo[5.2.1.0 2,6 ]dec-3-ene) derivative obtained from tricycle[5.2.1.0 2,6 ]dec-3-ene (8,9-dihydrodicyclopentadiene) and NBS with a good yield. The complete assignment of protons and carbons on nuclear magnetic resonance spectra was done for dicyclopentadiene and the chemically transformed compounds by 2D NMR techniques.
A new and practical synthesis of vinyl dichlorides via a non-Wittig-type approach
Tetrahedron Letters, 2000
A practical approach for the conversion of aldehydes to vinyl dichlorides has been developed. These are threestep, one-pot reactions involving the formation of trichlorocarbinol by treatment of aldehydes with trichloroacetic acid and sodium trichloroacetate followed by in situ protection and elimination reactions to form the desired vinyl dichlorides in 85 to 95% yields. tetl 16826 was added sodium trichloroacetate (119 g, 0.642 mol) in portions. The internal temperature was kept below 35°C by addition control. After addition was completed, the mixture was stirred at room temperature for 4 h with continuous evolution of CO 2 . The solution was cooled to 5°C and acetic anhydride (80.77 mL, 0.856 mol) was carefully added. Strong CO 2 evolution was observed. The mixture was allowed to warm to room temperature and stirred for an additional hour. The reaction mixture was diluted with acetic acid (400 mL) and cooled to 0°C. To the solution, the zinc powder (55.9 g, 0.856 mol) was added in one portion. The solution was stirred for 1 h at 60°C and then was cooled to room temperature. To the solution, water was added and then extracted with hexanes. The combined organic phases were washed with water and saturated aqueous solution of sodium chloride. The organic phase was dried over MgSO 4 , filtered and concentrated by rotary evaporation. The crude 1,1-dichloro-2-cyclopropylethylene was obtained in a relative good purity. Both flash chromatography (hexane:EtOAc, 9:1) and distillation (bp=47-5°C/2 torr) methods for the purification of this compound had been applied. Purification by distillation yielded 44.07 g (88%) of the desired compound, 4. Preparation of cyclopropylacetylene 1 (CPA) is a typical example for this procedure: To a stirred solution of 1,1-dichloro-2-cyclopropylethylene (29.10 mmol) in dried THF (40 mL) at −30°C was added MeLi (1.4 M in ether, 32 mmol, 1.2 equiv.) dropwise via an additional funnel. After the addition was completed, the solution was allowed to slowly warm to 0°C over a 1 h period. The reaction was quenched with saturated aqueous solution of ammonium chloride and diluted with heptane. The aqueous phase was extracted with heptane. The combined organic phases were washed with brine and dried over anhydrous MgSO 4 . After filtration a 95% solution yield of CPA in THF:heptane (1:6) was obtained. Fractional distillation at atmosphere pressure (b.p. 54-56°C) afforded neat CPA 1, 1.71 g (89%).
Tetrahedron Letters, 1994
Methyl cechlon-~ or a,adichloroastars are cbtained in excellent yields by oxidation chlorination of 2-alkyl-4,S-dimethyl-1,3-dioxolanes with trichl~socyanuric acid Esters of a,a-dichloro-carboxylic acids are use&l intemu&tes in the preparation of a-chloro-esters1 and of glycidic esters,2~3 through the Darzens reaction. General procedures for the synthesis of these dihaloeaters have been till now limited to the alkylation of dichloroacetates3 and to the Hell-Volhard-Zelinakii chlorination of carboxylic acids.5 However, the former method, though being more versatile, follows a very complicated procedure and the second one uses drastic reaction conditions. A preparation of a,a-dihaloesters by halogenation of ketene thioacetals has been alao reported, but without experimental detaih~ and yields.5
Preparation of trichloro- and tribromocyclopentadienyltungsten(IV)
Journal of Organometallic Chemistry, 2000
The thermal decarbonylation of (Ring)WX 3 (CO) 2 in refluxing toluene has led to the preparation of the CO-free compounds [(Ring)WX 3 ] 2 [Ring =h 5 -C 5 H 5 (Cp) and X =Cl (1a) or Br (1b); Ring =h 5 -C 5 H 4 Me (Cp%), X = Cl (2a) or Br (2b); Ring =h 5 -C 5 Me 5 (Cp*), X =Cl ]. The NMR properties of these molecules are consistent with diamagnetism and thereby indicate a different structure from that of the paramagnetic molybdenum analogues. Compounds 1a and 2a react with dppe to afford mononuclear 18-electron adducts, (Ring)WCl 3 (dppe) (Ring =Cp (4) or Cp% ). The X-ray structure of 5 shows a pseudo-fac-octahedral geometry with the dppe ligand occupying two equatorial (e.g. cis relative to Cp%) coordination sites. The X-ray structure of two by-products of the synthetic processes are also reported, e.g. Cp% 3 W 3 Cl 3 (m 2 -Cl) 2 (m 3 -O) (6) and [Cp*WCl 3 ] 2 (m-O) (7).
2010
Facile methods for the synthesis of isomeric triand tetramethyl-tetrahydrophenanthrenes (11, 18, 21, and 27) have been accomplished through rearranged Friedel-Crafts cycloalkylation of naphthylpentanols 1-4, respectively. Thus, treatments with the mild 85% H2SO4, H3PO4 and AlCl3/CH3NO2 catalysts produced 1,1,2-trimethyl-1,2,3,4tetrahydropenanthrene 11 from 2,2-dimethyl-5-(1-naphthyl)-3-pentanol 1, 3,4,4-trimethyl-1,2,3,4-tetrahydrophenanthrene 18 from 2,2-dimethyl-5-(2-naphthyl)-3-pentanol 2, 1,1,2,2-tetramethyl-1,2,3,4-tetrahydrophenanthrene 21 from 2,2,3trimethyl-5-(1-naphthyl)-3-pentanl 3 and 3,3,4,4-tetramethyl-1,2,3,4-tetrahydropenanthrene 27 from 2,2,3-trimethyl-5-(2naphthyl)-3-pentanol 4. Treatment with the strong AlCl3 catalyst resulted in varying amounts of side products. The starting and final products were characterized by elemental analysis and IR, H NMR and MS data.