Carbon novel forms

The formation of 2.6-octadienol (27) by the reaction of 1,3-butadiene with water has attracted attention as a novel method for the commercial production of n-octanol, which has a considerable market. However, the reaction of water under the usual conditions is very sluggish. The addition of CO2 facilitates the telomerizdtion of water and 2,6-octadienol (27) is obtained as a major pro-duct[31]. In the absence of CO2, only 1,3,7-octatriene (7) is formed. Probably octadienyl carbonate is formed, which is easily hydrolyzed to give 27. A com-... 

Shey J, CM McGinley, KM McCauley, AS Dearth, BT Young, WA van der Donk (2002) Mechanistic investigation of a novel vitamin Bjj-catalyzed carbon-carbon bond forming reaction, the reductive dimerization of arylalkenes. J Org Chem 67 837-846. 

A very attractive feature of radical chemistry is the generation of a novel radical after cyclization or any other radical translocation. This feature allows the inclusion of a second carbon—carbon bond-forming event and can, in principle, be extended even further. The resulting tandem reactions [38] can be extremely useful for the construction of complex molecules. Impressive early results have been reported by Stork in applications directed towards the synthesis of prostaglandins [39]. Our catalytic conditions also allow the realization of tandem reactions. An example including a mechanistic proposal is shown in Scheme 12.20. 

An obvious difference was also noted between control and induced skate hepaticdnicrosomal AHH activity in the presence of a-naphthoflavone (10 M). This compound, when added in vitro at this or higher concentrations, caused significant stimulation of AHH activity in control animals (about 3-fold) but inhibition (80%) was found in DBA-pretreated skates. Similar results were earlier reported for control and 3-methylcholanthrene-treated rats (23), where it appears that the response is due to differential effects of a-naphthoflavone on hepatic microsomal cytochrome P-450 (stimulated) and cytochrome P-448 (inhibited) (24). Our data suggests that there may be a novel form of cytochrome P-450 synthesized in skate liver in response to polycyclic hydrocarbon administration, even though there was no hypsochromic shift in the carbon monoxide difference spectrum of dithionite reduced hepatic microsomes from DBA-treated skates (relative to hepatic microsomes from control fish). 

The field of carbon nanostructure research is vast and novel, and it experienced a major breakthrough after the discovery of fullerenes in 1985 [1], and their subsequent bulk synthesis in 1990 [2]. This event opened the minds of various scientists towards discovering novel carbon allotropes. Promptly, yet another allotrop of carbon was observed by Iijima [3], although it had previously been produced by M. Endo et al. in the 1970s by chemical vapor deposition (CVD) [4]. The most recent important advance in the quest for novel forms of carbon constitutes the isolation of graphene layers [5], which exhibit unique and exceptional electrical properties [6]. In addition, graphene nanoribbons have recently been synthesized and produced using diverse methods [7]. 

In the absence of a proton donor, the alkoxide ion generated by carbanion addition to the carbonyl function can interact with a carbon-halogen bond in the 8 2 displacement reaction. Reactions of this type have led to some novel carbon chain forming processes. Ketones are converted to homologated enones in good yield by... 

Two novel forms of carbon, with formulas Qg [252] and [253] owe their stability to aromaticity with cyclic arrays of p orbitals which do not fall strictly into the class of cyclic systems discussed above ... 

Five years after the discovery of fullerenes, Iijima reported in 19911 a novel form of organized carbon which consists of hollow cylindrical structures, a few nanometers in diameter and some micrometers long. Although hollow carbon nanofibers had been prepared for several decades, their walls had never been resolved by High-Resolution Transmission Electron Microscopy (HRTEM). These HRTEM images allowed Iijima to conclude that the walls of the so-called multi-walled carbon nanotubes (MWCNTs) are made up of several concentric cylinders, each being formed by a graphene sheet rolled... 

Addition of diethylaminopropyne to C60 resulted in a [2+2] cycloadduct that can be ring-opened under acidic conditions, while, when followed by oxidative cy-clization in the presence of activated carbon, novel fullerene lactones were formed [62]. Further work on the reaction of C60 with propiolates in the presence of triph-enylphosphine resulted in the construction of bismethanofullerenes and a [2+2] cycloadduct consisting of a cyclobutane ring fused to a 6,6 ring junction [63]. 

The formation of a quaternary stereocenter could be achieved with a,a,a-trifluoroacetone as electrophile. An enantioselective procedure for this novel carbon-carbon bond-forming process has not been reported to date, the first results with a chiral imidazolium salt as precatalyst developed by Glorius et al. resulted in only low enantiomeric excesses (12-25% ee). 

In many cyclic aromatic compounds an element other than carbon (commonly N, O, or S) is also present in the ring. These compounds are called heterocycles. Figure 14.2.3 shows some nitrogen heterocycles commonly used as ligands, as well as planar, sunflower-like octathio[8]circulene, C Ss, which can be regarded as a novel form of carbon sulfide. 

The Ramberg-Backlund reaction, a novel carbon-carbon bond forming transformation, was discovered in 1940 when ethyl chloroethylsulfone 1, upon treatment with NaOH, was shown to form a mixture of cis and trans 2-butene. (Fig. 1) (7).The reaction has been used sporadically over the intervening years and has just received a comprehensive review in 2003.(2-8 )... 

Von Helden G, Hsu MT, Kemper PR, Bowers MT (1992) Novel forms of carbon. MRS Symposium Series.270 117... 

Basavaiah D, Rao PD, Hyma RS. The Baylis-Hillman reaction a novel carbon-carbon bond forming reaction. Tetrahedron 1996 52 8001-8062. 

A novel type of polymer-supported Lewis acid, a microencapsulated Lewis acid catalyst was investigated by Kobayashi [117]. Sc(OTf)3 was immobilized on to polystyrene by microencapsulation—Sc(OTf)3 is physically enveloped by polystyrene and stabilized by the interaction between the jr-electrons of benzene rings and vacant orbitals of the Lewis acid. This microencapsulated catalyst was used successfully in several Lewis acid-catalyzed carbon-carbon bond-forming reactions (imino aldol, aza Diels-... 

Solids of elemental carbon in the sp bonding state can form a variety of graphitic structures. Graphite filaments can be produced, for instance, when amorphous carbon filaments formed by thermal decomposition of hydrocarbon species are subsequently graphitized by heat treatment. Graphite filaments can also grow directly from the vapour-phase deposition of carbon s ll which also produces soot and other novel structures such as the C i molecule. ... 

The existence of a form of solid carbon where carbynoid species can coexist with sp hybridization has important implications for the achievement of a deeper understanding of the processes leading to the formation of carbon clusters [46], for the synthesis of novel carbon allotropic forms and nanomaterials [1], and for the chemistry of the interstellar medium [12]. 

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