Carbon insertion

Single-Carbon Insertion Reactions. Carbonylation, cyanidation, and "DCME," and related reactions are convenient general processes developed to bring about the transfer of organic groups from boron to a siagle-carbon atom. 

Diaminopyrimidines fused to a number of heterocycles (35) were also cyclized with one-carbon inserting agents to the corresponding hetero-cyclo-l,2,4-triazolo[l,5-c]pyrimidines 36 (75M1111 81JHC43 97JIC27). 

It is worth noting that the 2-pyridone 42 (99MI1) and thione 43 (88H(27)733), which could react in either of the two ways as shown, with an isocyanate or isothiocyanate and with a nitrile respectively, actually give a one-carbon insertion. There is a case of formation of 2,3 and 3,4 bonds in the preparation of 8-hydroxy-triazolopyridine 44 (83MI1). 

Cyclization of the hydrazone derivatives of 4-benzoyl[ 1,2,3]triazole 695 by reaction with one carbon inserting agent such as an orthoester, an aldehyde, a ketone, or a phosgene afforded triazolotriazine 696 or 697 (88JHC743). The newly created C—N bond displays particular sensitivity due to the electron-attracting effect of the triazole ring (Scheme 147). 

Perhaps the synthesis of hydrocarbons is best understood. There are three main classes of reactions leading to complex hydrocarbons carbon insertion, condensation, and radiative association. Carbon insertion reactions are between C+ ions and smaller hydrocarbon neutrals viz.,... 

Products in several isomeric forms can occur in systems with fewer atoms than considered above the association reaction between C3H+ and H2 to produce both cyclic and noncyclic C3H3 is a case in point, although the branching ratio in this instance seems to be noncontroversial.30 The problem of whether product hydrocarbon ions are cyclic or noncyclic extends to other classes of ion-molecule reactions such as condensation and carbon insertion reactions, where studies of product reactivity have only been undertaken in a few instances. In general, cyclic ion products are less reactive than their noncyclic counterparts. For systems with a... 

The mechanism for the formation of complex hydrocarbons through fullerenes is loosely taken from Helden et al.119 and Hunter et al.,120 and is depicted in Figure 2. As in the work of Thaddeus,117 linear carbon clusters grow via carbon insertion and radiative association reactions, although in this case a large number of additional reactions involving neutral atoms such as C, O, and H and neutral molecules such as H2 are also included. Reactions with H and H2 serve to produce... 

Reaction of 768 with one carbon inserting agents, such as formic acid or carbon disulfide, gave (89MI1) 769 and 770, respectively. Methylation of 770 gave 771. 

The last class of reactions is of importance for the formation of organic molecules and organic polymers. The carbon insertion reactions (Figure 5.11, reaction (i)) are ion-molecule reactions and so are favoured at low temperatures and result in the... 

A complex chain of carbon insertion reactions is thought to initiate the formation of PAHs in the ISM and on the surface of dust grains by the formation of carbon chains ... 

It is tempting to take the carbon insertion mechanisms to the extreme and look for the completely unsaturated carbon allotropes of graphite and diamond. Graphite has been postulated for many years but there is at present no IR evidence for it in the ISM. This is partly due to the problems of detection. The gross selection rule for an IR spectrum requires a change in dipole moment during a vibration and the... 

Carbon insertion reaction The addition of a carbon atom to an existing carbon chain, usually by a radical reaction mechanism. 

Single-base propellants, 10 725 Single-carbon insertion reactions in organoboranes, 13 654—657 Single-cell drum filters, 11 357 Single-cell protein(s) (SCP), 13 688,16 315, 26 474... 

Kuethe et al. reported the synthesis of the tjipanazoles D (359), I (360), B (369), and E (370) starting from the nitro derivative 1496 (796). This route involves the synthesis of 2,2 -bisindoles, followed by a two-carbon insertion through condensation with (dimethylamino)acetaldehyde diethyl acetal to afford the indolocarbazole ring. 

A completely different approach was used to probe the reactivity of tert-butyl-carbene, one of Frey s original examples. Table 7.6 shows the varying products of thermal and photochemical decomposition of the diazo compound. It would appear that carbon-hydrogen insertion and carbon-carbon insertion are about equally facile in the carbene presumed to be formed in photolytic reactions. Even in 1964, this observation should have seemed strange (as it clearly did to... 

Frey), as there was no known example of an intermolecular carbon-carbon insertion. The ensuing decades have not revealed such a reaction, despite some hard searching. " Why should the intramolecular version of carbon-carbon insertion compete so favorably with carbon-hydrogen insertion It doesn t. Two alternative... 

A similar story attends the chemistry of cyclopropylcarbenes. In the 1960s it was shown that cyclopropyl methyl diazomethane gives almost exclusively the product of apparent carbon-carbon insertion. " Surely we are now suspicious, and rightly so, as neither photolysis of 62 nor deoxygenation of cyclopropyl methyl ketone reproduces these results. Instead, carbon-hydrogen insertion dominates (Scheme 7.25). Once again, a direct reaction of photoexcited diazo compound appears to be the dominant source of the product of ring expansion (carbon-carbon insertion). 

Although the chemistry of the initial thermal transformation is obviously quite complex, it was determined that considerable carbon insertion into the Si-Si bonds occurs, resulting in an intermediate carbosilane which can be drawn into fibers. At this point, brief oxidation results in the formation of a surface oxide which imparts dimensional stability, and subsequent heating to 1300°C produces silicon carbide fibers (3,5). 

Carbon materials used for the commercial synthesis of carbon fluoride include natural graphite, petroleum coke, activated carbon, carbon black and carbon fiber. Experimental carbon materials include residual carbon, exfoliated graphite, fullerenes and other unique carbons and carbon inserts. The degree of graphitization of carbon material varies continuously, so it is not simple to define the exact boundary between carbon and graphite. The product formed... 

Treatment of salicylic hydrazide in toluene with a single carbon insertion unit, such as carboxylic acid anhydride, acid chloride, and orthoester, in the presence of an equimolecular amount of methanesulfonic acid gave the l,3,4-benzoxadiazepin-5-ones (530) (43-68% yield), via the O-acylation intermediates (529) (92S929). 

For siletanes with tertiary carbons, insertion into a C-H is favored over a Si-C insertion <1967JA1538>. 

When carbon electrodes are used, Li may be inserted/intercalated reversibly into the carbon at potentials as high as 1 V versus Li/Li+ (after the formation of surface films). In the case of disordered carbons, insertion may occur at even higher potentials. In the case of graphite (as described in the next section), the onset for lithium intercalation is around 0.3 V versus (Li/Li+). With glassy carbon, there is no considerable lithium insertion, and hence this electrode behavior depends solely on the solvent and anion used and their cathodic stability [28],... 

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