Carbonation direct

The methine chain is obtained by reacting ethyl o-formate (method A ) or ethylisoformanilide (method B) with a bis quaternary salt of bis-(2-thiazolyllbutane. Concerning dyes with fused thiazolo rings pyrrolo[2. lb]thiazoIe. thiazolo[2.3a]indole. thiazolo[2.3c]1.4-benzox-azine. the a carbon directly linked to the carbon 2 of the thiazoJe ring is also responsible for the classical syntheses giving trimethine or penta-methine dyes. 

Benzylic carbon (Section 11 10) A carbon directly attached to a benzene nng A hydrogen attached to a benzylic carbon is a benzylic hydrogen A carbocation in which the benzylic carbon is positively charged is a benzylic carbocation A free radical in which the benzylic carbon bears the unpaired electron is a benzylic radical Benzyne (Section 23 8) The compound... 

Disubstituted alkene (Section 5 6) Alkene of the type R2C=CH2 or RCH=CHR The groups R may be the same or different they may be any length and they may be branched or unbranched The significant point is that there are two carbons directly bonded to the carbons of the dou ble bond... 

Monomer (Section 6 21) The simplest stable molecule from which a particular polymer may be prepared Monosaccharide (Section 25 1) A carbohydrate that cannot be hydrolyzed further to yield a simpler carbohydrate Monosubstituted alkene (Section 5 6) An alkene of the type RCH=CH2 in which there is only one carbon directly bonded to the carbons of the double bond Multiplicity (Section 13 7) The number of peaks into which a signal IS split in nuclear magnetic resonance spectroscopy Signals are described as singlets doublets triplets and so on according to the number of peaks into which they are split... 

Synthetic Resins. Various polymers and resins are utilized to produce some specialty carbon products such as glassy carbon or carbon foam and as treatments for carbon products. Typical resins include phenoHcs, furan-based polymers, and polyurethanes. These materials give good yields of carbon on pyrolysis and generally carbonize directly from the thermoset polymer state. Because they form Httle or no mesophase, the ultimate carbon end product is nongraphitizing. 

M-Acyliminium cyclizations of optically active mono- and di-oxygenated hydroxylactam derivatives have been used in the synthesis of a number of natural products. In case of a five-membered lactam the oxygen function adjacent to the iminium carbon directs attack of the internal nucleophile from the least hindered side, opposite to the substituent. In the examples given the size of the newly formed ring is determined by the electronic bias of the alkene substituent. 

Carbon dioxide carryover also occurs following the deliberate addition of soda ash (sodium carbonate) directly to the boiler. Where boiler designs provide for a significant internal drum or shell, the use of soda ash and caustic soda to prevent calcium and magnesium scales by precipitation reactions (internal softening) may be employed. 

If the carbanion has even a short lifetime, 6 and 7 will assume the most favorable conformation before the attack of W. This is of course the same for both, and when W attacks, the same product will result from each. This will be one of two possible diastereomers, so the reaction will be stereoselective but since the cis and trans isomers do not give rise to different isomers, it will not be stereospecific. Unfortunately, this prediction has not been tested on open-chain alkenes. Except for Michael-type substrates, the stereochemistry of nucleophilic addition to double bonds has been studied only in cyclic systems, where only the cis isomer exists. In these cases, the reaction has been shown to be stereoselective with syn addition reported in some cases and anti addition in others." When the reaction is performed on a Michael-type substrate, C=C—Z, the hydrogen does not arrive at the carbon directly but only through a tautomeric equilibrium. The product naturally assumes the most thermodynamically stable configuration, without relation to the direction of original attack of Y. In one such case (the addition of EtOD and of Me3CSD to tra -MeCH=CHCOOEt) predominant anti addition was found there is evidence that the stereoselectivity here results from the final protonation of the enolate, and not from the initial attack. For obvious reasons, additions to triple bonds cannot be stereospecific. As with electrophilic additions, nucleophilic additions to triple bonds are usually stereoselective and anti, though syn addition and nonstereoselective addition have also been reported. 

The F coupling to carbon can vary considerably for the carbon directly substituted (ipso), depending on its substitution environment, but it is always very large, 250 Hz or larger. F coupling to the ortho-position is usually about 20-26 Hz, to the raeta-position about 8-10 Hz, and to the para-position about 4 Hz. 

Another approach toward C-O bond formation using alkynes that has been pursued involves the intermediacy of transition metal vinylidenes that can arise from the corresponding y2-alkyne complexes (Scheme 13). Due to the electrophilicity of the cr-carbon directly bound to the metal center, a nucleophilic addition can readily occur to form a vinyl metal species. Subsequent protonation of the resulting metal-carbon cr-bond yields the product with anti-Markovnikov selectivity and regenerates the catalyst. 

The substitutions at C-l can be classified as processes with umpolung of reactivity since a negatively charged carbon directly connected to oxygen is involved. A variety of synthons with umpolung of reactivity are therefore derived from simple alkoxyallenes as summarized in Scheme 8.4. The rich and often very surprising chemistry of these unique, but easily available, building blocks is still under development and it is expected that even more new synthons derived from alkoxyallenes will be detected in the future. 

The existence of surface hydride groups of the types known in classic organic chemistry is very probable in most carbons. Direct chemical evidence is very difficult to obtain due to the relative inertness of the carbon-hydrogen bond. However, the fact that hydrogen is strongly chemisorbed on carbons and released at high temperatures only in the form of hydrocarbons is sufficient proof of the existence of true carbon-hydrogen bonds. 

An improved route to milnacipran (2) and derivatives is described in Scheme 14.5. In this approach, lactone 20 was opened with lithium diethylamide to provide amide alcohol 25, which was readily transformed into azide 26. Hydrogenation on palladium-carbon directly led to the desired target in 86% yield over the three steps. 

Figure 2.16 The structure of tetraphenylmethane the view down any phenyl-central carbon direction is that of a propeller...

The first organometallic compound of the transition metals to be characterized (1827) was Zeise s salt, K[(C2H4)PtCl3]-H20 (Fig. 18.1). It forms when K2[PtCl4] in aqueous ethanol is exposed to ethylene (ethene) a dimeric Pt—C2H4 complex with Cl bridges is also formed. In both species, the ethylene is bonded sideways to the platinum(II) center so that the two carbon atoms are equidistant from the metal. This is called the dihapto-or T]2 mode. A ligand such as an allyl radical with three adjacent carbons directly bonded to a metal atom would be trihapto- or t 3, and so on. 

The similarity in the pyrimidine carbon resonances in cytidine and deoxycytidine is indicative of the independence of these shifts from the sugar fragments. The differences observed between the chemical shifts of uracil and thymine, or uridine and thymidine, indicate that they must result from the presence of the 5-methyl group in the latter. The downfield shifts ( — 7.5 ppm) of the 05 peaks of uracil or uridine upon 5-methyl substitution are typical for a carbon directly substituted by a... 

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