cas 1000-86-8, 2,4-DIMETHYL-1,3-PENTADIENE

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Courtot
p. 984
()
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Direct episulfidation of alkenes and allenes with elemental sulfur and thiiranes as sulfur sources, catalyzed by molybdenum oxo complexes
The molybdenum oxo complexes 1a and 1b catalyze efficiently the sulfur transfer to a series of alkenes 4 and allenes 6, for which elemental sulfur, phenylthiirane, or methylthiirane have been employed as sulfur sources to afford the corresponding episulfi
Adam, Waldemar,Bargon, Rainer M.,Schenk, Wolfdieter A.
p. 3871 - 3876
(2003)
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Pentadienyluranium borohydride complexes and their cyclopentadienyl analogues; crystal structures of (η-2,4-Me2C5H5)U(BH4)3 and (η-C5H5)U(BH4)3
Treatment of U(BH4)4 (I) with the potassium salt of the 2,4-dimethylpentadienyl anion (dmpd) afforded the pentadienyl complex (dmpd)U(BH4)3 (II), whereas the reaction of (dmpd)3U (VI) with TlBH4 gave (dmpd)2U(BH4)2 (IV).Complex VI reacted with KBH4 in the presence of 18-crown-6-ether to give the anionic uranium(III) compound (VII), and the corresponding cyclopentadienyl derivative (VIII) was obtained from the Na/Hg reduction of Cp2U(BH4)2 (V).The open pentadienyl ligand of these complexes was found to be less strongly bound to the metal centre than its cyclic counterpart in the corresponding cyclopentadienyl derivatives.The crystal structures of the pseudo-tetrahedral II and CpU(BH4)3 (III) complexes show that the U-C-(pentadienyl) bonds are longer than the U-C (cyclopentadienyl) bonds, and that there is a large degree of ionic character in the metal-pentadienyl bonding.
Baudry, Denise,Bulot, Emmanuelle,Charpin, Pierrette,Ephritkhine, Michel,Lance, Monique,et al.
p. 163 - 174
(1989)
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Tetramethylallene and 2,4-Dimethyl-1,3-pentadiene as Hydrogen Atom Acceptors in Reactions with HMn(CO)5 and HCo(CO)4
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Garst, John F.,Bockman, T. Michael,Batlaw, Rajnish
p. 1689 - 1691
(1986)
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Synthesis and X-ray crystal structure of a cationic gold (I) π-(1,3-diene) complex generated via isomerization of a gold π-allene complex
The cationic gold tetramethylallene complex {[P(t-Bu)2o- biphenyl]Au(η2-Me2CCCMe2)}+ SbF6- (1) underwent formal 1,3-hydrogen migration in CD2Cl2 solution at
Brown, Timothy J.,Robertson, Bradley D.,Widenhoefer, Ross A.
p. 25 - 28
(2014)
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Elliott,Frey
p. 345,346
(1965)
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Metallaborane reactivity. A stoichiometric mechanism for the insertion of two alkynes into an iridaborane framework via a disposable molybdenum chaperone
Building on earlier work that showed the formation of [1-Cp*-2,2,2- (CO)3-2-THF-nido-1,2-IrMoB4H8], 2, from the reaction of [1-Cp*-arachno-1-IrB4H10], 1, with (arene)Mo(CO)3, the stoichiometric mechanism for the generation of [1-Cp*-5,6,7,8-(R)4-nido-1,5,6,7,8-IrC4B 3H3], 8, from the reaction of 2 with RC≡CR, R = Me, Ph, has been identified. For R = Me, the major product in solution is [1-Cp*-5,6,7,8-(CH3)4-closo-1,5,6,7,8-IrC 4B3H3Mo(CO)3], 7, which is in equilibrium with 8. The equilibrium 8 + Mo(THF)3-(CO)3 ? 7 + 3THF is characterized by ΔH = 8 kcal/mol and ΔS = 34 cal/mol K. Density functional theory calculations carried out on 7 indicate that the Mo(CO)3 moiety is weakly bound to the cluster mainly through Mo-C rather than Mo-B interactions. Under alkyne deficient conditions, the product [1-Cp*-2,2,2-(CO)3-(μ-CO)-3,4-(CH3) 2-closo-1,2,3,4-IrMoC2B3H3], 6, can be isolated. Solid-state structures of 1 and 2 have been reported previously, and those of 6, 7, and 8, R = Me, Ph, are reported here. The evolution of products with time was monitored by 1H and 11B NMR and showed the formation and decay of two additional species which have been identified as the structural isomers [1-Cp*-7,7,7-(CO)3-7-THF- 2,3-(CH3)2-nido-1,7,2,3-IrMoC2B 3H5], 4, and [5-Cp*-7,7,7-(CO)3-7-THF-2, 3-(CH3)2-nido-5,7,2,3-IrMoC2B3H 5], 5, with the metals nonadjacent in 4 and adjacent in 5. Circumstantial evidence suggests that 4 is the precursor to 5 and 5 is the precursor to both 6 and 7. Cluster 2 also is a catalyst or catalyst precursor for the isomerization of olefins, namely, hex-1-ene to cis-hex-2-ene and tetramethyl allene to 2,4-dimethylpenta-1,3-diene. These novel results also establish that [1-Cp*-2,2,2-(CO)3-2-(alkyne)-nido-1,2- IrMoB4H8], 3, forms from 2 and constitutes a logical precursor to 4. The entire process, 1 + 2alkyne = 8 + BH3 + 2H 2, which is promoted by (arene)Mo(CO)3, constitutes an explicit example of a transition-metal-facilitated process analogous to metal-facilitated organic transformations observed in organometallic chemistry.
De Montigny, Frederic,Macias, Ramon,Noll, Bruce C.,Fehlner, Thomas P.,Costuas, Karine,Saillard, Jean-Yves,Halet, Jean-Francois
p. 3392 - 3401
(2007/10/03)

Catalytic hydromagnesation of di- and polymethyl-substituted 1,3-butadienes
Hydromagnesation of di- and polymethyl-substituted 1,3-butadienes with alkylmagnesium halides in the presence of Ni(PPh3)2Cl2 and NiPy4Cl2 was studied.
Viktorov,Zubritskii
p. 1755 - 1765
(2007/10/03)

Surface-Mediated Reactions. 6. Effects of Silica Gel and Alumina on Acid-Catalyzed Reactions
Absorption of a variety of acids to chromatographic silica gel results in substantial enhancement of their catalytic activity-affording easily prepared, environmentally benign heterogeneous acids that are highly effective in mediating a number of processes.This was shown for the isomerization of allene 1 and dimerization of the corresponding 1,3-diene 2; cyclization of (R)-citronellal (5), the related diester 10, and 1,5-cyclooctadiene (15); Rupe rearrangement of alkynol 18; and Friedel-Crafts cyclodehydration of alcohols 21.By contrast, commercially available Nafion-H was significantly less effective as a heterogeneous acid catalyst.Chromatographic alumina displayed enigmatic behavior, showing enhanced acidity on the adsorption of HCl but little or no acidity on the adsorption of a variety of other types of acid.The results are discussed in terms of the surface structures of silica gel and alumina.
Kropp, Paul J.,Breton, Gary W.,Craig, Stephen L.,Crawford, Scott D.,Durland, William F.,et al.
p. 4146 - 4152
(2007/10/02)

Pentadienyl-metal-phosphine chemistry. 9. The 2,4-dimethylpentadienyl-iron-trimethylphosphine reaction system
The reaction of FeCl2(PMe3)2 with potassium 2,4-dimethylpentadienide-tetrahydrofuran (K+2,4-Me2pd-) can be directed into three separate manifolds by varying the ratio of K+2,4-Me2pd- to iron. Use of a 2:1 K+2,4-Me2pd-:Fe ratio leads to the production of (η5-2,4-Me2pd)(η3-2,4-Me 2pd)Fe(PMe3) (1) while a 1:1 K+2,4-Me2pd-:Fe ratio yields (η4-isopropenyltrimethylenemethyl)Fe(PMe3)3 (2) via a reaction sequence involving activation of a C-H bond in a 2,4-Me2pd methyl group. When the ratio of K+2,4-Me2pd-:Fe is reduced to 1:2, (η5-2,4-Me2Pd)Fe(PMe3)3 +FeCl3(PMe3)- (3) is produced. Single-crystal X-ray diffraction studies of both 2 and 3 have been carried out. Compound 2 crystallizes in the monoclinic space group P21/c with a = 8.878 (1) A?, b = 14.737 (4) A?, c = 16.689 (3) A?, β = 102.25 (1)°, V = 2129.5 (8) A?3, and Z = 4. The complex assumes an approximate octahedral geometry with C1, C3, and C6 of the isopropenyltrimethylenemethyl ligand (iTMM) and the three phosphine phosphorus atoms occupying the six coordination sites. The iTMM ligand exhibits an umbrella shape with C2 bent out of the C1/C3/C6 plane. Compound 3 crystallizes in the monoclinic space group C2/c with a = 18.442 (5) A?, b = 18.433 (5) A?, c = 17.875 (5) A?, β = 91.87 (2)°, V = 6073 (3) A?3, and Z = 8. The coordination geometry of the cation is approximately octahedral with C1, C3, and C5 of the 2,4-Me2pd ligand and P1, P2, and P3 of the PMe3 ligands occupying the six coordination sites. The anion of 3, FeCl3(PMe3)-, adopts an ethane-like geometry with the three chloro ligands on iron and the three methyl groups on phosphorus arranged in a staggered orientation. The reaction of 1 with HO3SCF3 and 2 equiv of PMe3 in diethyl ether produces (η5-2,4-Me2Pd)Fe(PMe3)3 +O3SCF3- (4). In solution, the η5-2,4-Me2Pd ligand in 4 rotates with respect to the Fe(PMe3)3 fragment. Line-shape simulations of the variable-temperature 31P{1H} NMR spectra have enabled us to calculate a ΔG≠ of 11.5 ± 0.5 kcal for this process.
Bleeke, John R.,Hays, Mary K.
p. 486 - 491
(2008/10/08)

SYNTHESIS OF SOME 3-SUBSTITUTED-2,4-DIMETHYL-1,3-PENTADIENES
Pyrolysis of various 1-bromo-2,2,3,3-tetramethylcyclopropanes leads to the corresponding 3-substituted-2,4-dimethylpenta-1,3-dienes in good yield.
Warner, Philip M.,Le, Diem
p. 1341 - 1348
(2007/10/02)

Lewis Acid Catalysed Addition Reactions of 1,3-Alkyl Substituted Allyl Chlorides with Alkenes
The zinc chloride-ether catalysed reactions of 2-unsubstituted allyl chlorides (5) with alkenes (6) yield linear addition products (7) which may undergo two types of sequential reactions: Electrophilic additions to alkenes (allyl chloride induced polymeri
Mayr, Herbert,Klein, Herbert,Kolberg, Gerlinde
p. 2555 - 2579
(2007/10/02)

Preparation, Pyrolysis, and Photolysis of Three Sterically Crowded Alkenes, 3,3,3',3',5,5,5',5'-Octamethyl-3,3',5,5'-tetrahydro-4,4'-bi(4H-pyrazolylidene) 2,2,4,4-Tetramethyl-3-(3,3,5,5-tetramethyl-3,5-dihydro-4H-pyrazol-4-ylidene)-thietane 1,1-Dioxide and 2,2,2',2',4,4,4',4'-Octameth...
Photolysis and pyrolysis of the title compounds involve a stepwise elimination of nitrogen and/or sulphur dioxide and reactions which can be interpreted in terms of a series of trimethylenemethane (TMM) biradical intermediates.However, the photosensitised photolysis of the bi(pyrazolylidene) (11) give products indicative of an elimination of both nitrogens and the generation of a tetramethylene-ethane (TME) biradical intermediate.New synthesis of a number of highly sterically crowded alkenes including 2,2,4,4-tetramethyl-3-(3,3,5,5-tetramethyl-3,4-dihydro-4H-pyrazol-4-ylidene)thietane 1,1-dioxide (12) and 2,2,2',2',4,4,4',4'-octamethyl-3,3'-bithietanylidene 1,1,1',1'-tetraoxide (13), are described.Flash vacuum pyrolysis (f.v.p) of 3,3,3',3',5,5,5',5'-octamethyl-3,3'-5,5'-tetrahydro-4,4'-bi(4H-pyrazolylidene) (11) at 400 deg C gives 3,3,5,5-tetramethyl-4-(2,2,3,3-tetramethylcyclopropylidene)-3,5-dihydro-4H-pyrazole (21), at ca. 400 deg C 1-isopropylidene-2,2,4,4,5,5-hexamethylspiropentane (22), and at ca. 580 deg C a ca. 5:1 mixture of 4-isopropyl-3-isopropylidene-2,5-dimethylhexa-1,4-diene (23) and 2-(2,3-dimethylbut-1-en-3-yl)-1-isopropyl-3,3-dimethylcyclopropene (27).Above 700 deg C a complex mixture of aromatic products and low molecular weight hydrocarbons is produced which includes ethane, ethylene, propene, isobutane, and isobutene, p-xylene, o-cumene and probably m-cumene, and 2,5-dimethylisopropylbenzene.F.v.p. of the dihydropyrazole sulphone (12) gives initially 2,2,4,4-tetramethyl-3-(2,2,3,3,-tetramethylcyclopropylidene)thietane 1,1-dioxide (41) and at higher temperatures similar mixtures to those obtained from the bipyrazolylidene (11).Similar results were also obtained for the f.v.p. of the bis-sulphone (13).Photolysis of the bipyrazolylidene (11) gave initially the dihydropyrazole (21) and then a 48:52 mixture of the spiro compound (22) and 2,2,2',2',3,3,3',3'-octamethylbicyclopropylidene (42).Photolysis of the dihydropyrazole sulphone (12) gave 2,2,4,4-tetramethyl-3-(2,2,3,3-tetramethylcyclopropylidene)thietane 1,1-dioxide (41).Benzophenone-sensitised photolysis of the bipyrazolylidene (11) gave 1,2-di-isopropylidene-3,3,4,4-tetramethylcyclobutane (32).
Bushby, Richard J.,Mann, Stephen,Jesudason, Malini, V.
p. 2457 - 2464
(2007/10/02)

Photochemistry of Alkyl Halides. 10. Vinyl Halides and Vinylidene Dihalides
The photobehavior of the acyclic vinyl iodide 2, the 1-iodocycloalkenes 11-14 and 39, the (halomethylene)cycloalkanes 45-48, and the (dihalomethylene)cyclohexanes 62-64 has been studied.Except for the dichloride 64, which exhibited only radical behavior, each of the halides afforded a mixture of ionic and radical products.The two bromides studied, 48 and 63, afforded lower ratios of ionic to radical products than the corresponding iodides 45 and 62.Irradiation of vinyl iodides was found to be a convenient and powerful method for the generation of vinyl cations, including the highly strained 1-cyclohexenyl and 1-cyclopentenyl cations and the unstabilized α-unsubstituted cations 51 and 54.The latter cations underwent rearrangement to the ring-expanded 1-cycloalkenyl cations 28 and 36, respectively.Lowering the temperature of the irradiation of iodides 13, 14, and 45 resulted in an increased ratio of ionic to radical products.However, iodide 47, which underwent principally fragmentation to enyne 61, showed little temperature effect.
Kropp, Paul J.,McNeely, Steven A.,Davis, Robert Drummond
p. 6907 - 6915
(2007/10/02)