Protonation and Alkylation of

According to calculations, this new anion should have a structure where two B12Hn units are joined by a 3c2e B-H bond. 

Halogenation of the B12Hi22- ion with N-halosuccinamide leads to mono- and di-halosubstituted dodecaborates, while reaction with elemental halogens finally led 

The dodecahalogeno-closo-dodecaborates Bi2Xi22 can be oxidatively transformed into polyboranes BnXn. However, the anions proved not to be suitable for developing a chemistry of their own, e.g., polymers based on Bi2 units or dendrimers. Therefore, functional hydro-closo-dodecaborates carrying reactive substituents are needed. 

Moreover, B 2(OH) 22 can also perbenzylated with benzylchloride in the presence of EtNPrl2 under reflux in acetonitrile. The alkylation requires 6 days [see Eq. (72)]. Shorter reaction times result in incomplete reaction, longer ones in the formation of larger quantities of the purple radical anion [B 2(OCH2Ph) 2. This radical can also be generated by a one electron oxidation with Fe3+, and it is even possible to further oxidize the radical anion to the dark orange neutral hyper-doso-B12(OCH2Ph)i2 [121]  

Amination of B12H122 requires the electrophile hydroxylamine-O-sulfonic acid. Besides Bi2Hn(NH3), the main product is 1,7-Bi2Hio(NH3)2 [122]. In both compounds, the B-N bond lengths are shorter than in Bi2HnNEt3. 

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A parallel exists between the results of protonation and alkylation of pyrazolones since there is an alkyl derivative for each tautomer. The main difference is that the percentage of the different tautomers is thermodynamically controlled whereas that of alkyl derivatives is kinetically controlled. One has to remember that the alkyl derivatives thus obtained are the fixed compounds used in tautomeric studies. 

Protonation and alkylation of the anhydro-bases (e.g. 425) takes place at the ind-N atom (see Section IV, A, 2). The resulting ind-N-, j92/r-A-dialkylcarbolinium salts (e.g. 426) give the corresponding... 

X-ray analysis has been successfully used for elucidation of the structures obtained in the oxidation and alkylation reactions of 5-phenyl-l,2,3,4-thiatriazole <1976ACA351>, and to determine the place of protonation and alkylation of l,2,3,4-thiatriazole-5-thiolate <2004IC1370>. The structures of l,2,3,4-thiatriazol-5-thiolate derivatives as heterocyclic pseudohalides were carefully studied by the X-ray diffraction method <2000JA9051, 2004IC1370>. 

Protonation and alkylation of arenes afford cyclohexadienyl cations (arenium ions) which are also of importance in electrophilic aromatic substitution. The hepta-methylbenzenium ion (16) is a very stable species30-, but even the parent benzenium ion (17a) has been observed as have most of its alkyl, halo, and alkoxy derivatives51. The benzenium ion (17a) undergoes a rapid degenerate rearrangement which equilibrates the seven protons over six carbons. Data for the monosubstituted benzenium ions show that (17) is the most stable of the possible isomeric forms. Positive charge... 

The CNDO/2 method has been used for the calculation of the sites of the protonation and alkylation of 1,2,4-triazines <88KGS525>. It was also applied to calculate the two-photon tensor invariants proportional to two-photon absorptivities for transitions to the lowest singlet states, Lb (B2 -) and L/ (B,/) <84CPL(107)125>. 

The ordering of the electronic transitions in the (phosphine)2Pt S2C2(Het) (R ) complexes depends on the appended heterocycle. For these complexes the energy of the ILCT transition tracks with the reduction potential and hence the electron affinity of the heterocycle [30]. Consistent with this observation, the energy of the transition is lowei by protonation and alkylation of the heterocycle (see Section VI) [30-35]. 

The structure of the carboxylated derivative of the addition product tvas proven from a mixed melting point determination with an authentic sample. K6-brich and Stober [21] reinvestigated this reaction in tetrahydrofuran (THF) at -80 to 20 °C and isolated a,a-diphenylheptanoic acid in 98% yield protonation and alkylation of the intermediate 1,1-diphenylhexyllithium with water and n-butyl bromide formed 1,1-diphenylhexane and 5,5-diphenyldecane in 99% and 97% yields, respectively. However, Evans and George [22] have reported that further reversible addition can occur when a large molar excess (6.4-fold) of 1,1-diphenylethylene is reacted with -butyllithium in benzene at 30 °C as shown in Scheme 1. The amount of 1,1,3,3-tetraphenyloctane isolated after hydrolysis was much less than the amount of 1,1-diphenylhexane therefore it was concluded that the second equilibrium step in Scheme 1 strongly favors the monoadduct. No 1,1,3,3-tetraphenyloctane was detected when only a 1.8-fold excess of DPE was used [22, 23]. From the kinetics of the reaction it was concluded that the addition of n-butyllithium to DPE is irreversible [23]. 

The chemical behaviour of the mesoionic pyrazole (459) has been studied by Boyd et al (74JCS(P1)1028). Protonation and alkylation take place on the exocyclic nitrogen atom and a thermal rearrangement of a methyl group is observed when (459) is boiled in benzonitrile for several hours giving (460). 

Two methods for converting carboxylic acids to esters fall into the mechanistic group under discussion the reaction of carboxylic acids with diazo compounds, especially diazomethane and alkylation of carboxylate anions by halides or sulfonates. The esterification of carboxylic acids with diazomethane is a very fast and clean reaction.41 The alkylating agent is the extremely reactive methyldiazonium ion, which is generated by proton transfer from the carboxylic acid to diazomethane. The collapse of the resulting ion pair with loss of nitrogen is extremely rapid. 

Polyene Cyclization. Perhaps the most synthetically useful of the carbo-cation alkylation reactions is the cyclization of polyenes having two or more double bonds positioned in such a way that successive bond-forming steps can occur. This process, called polyene cyclization, has proven to be an effective way of making polycyclic compounds containing six-membered and, in some cases, five-membered rings. The reaction proceeds through an electrophilic attack and requires that the double bonds that participate in the cyclization be properly positioned. For example, compound 1 is converted quantitatively to 2 on treatment with formic acid. The reaction is initiated by protonation and ionization of the allylic alcohol and is terminated by nucleophilic capture of the cyclized secondary carbocation. 

IV. PROTONATED AND ALKYL CATIONATED AMINES A. Formation and Properties of Protonated and Alkyl Cationated Amines... 

Cyclic analogues of hydrazones [151], 2-pyrazolines, show both protonation and alkylation on N-1, as has already been discussed on page 326. The sp nitrogen (which distinguishes these systems from enamines) does not appear to play any direct part. 

The largest number of hydrogen bonds in crystal structures of alkyl hydroperoxides refer to intermolecular bonds between the hydroperoxide proton and functionalities of the type 0=X, where X denotes a sulfur (e.g. 27), carbon (e.g. 30) or a phosphorous atom (e.g. 32, Figure 14, Table 7)93,108,115 geometry of [l,2-bis(diphenylphosphinoyl)ethane] bis(2,2-dihydroperoxypropane) (32) in the solid state is a rare example of a bifurcated hydrogen bond between an OOH donor and an 0=X proton acceptor. 

Isoquinoline, like quinoline, is protonated and alkylated at the nitrogen atom, but electrophilic substitution in the benzene ring is also easily achieved (Scheme 3.14). Sulfonation with oleum gives mainly the 5-sulfonic acid, but fuming nitric acid and concentrated sulfuric acid at 0 C produce a 1 1 mixture of 5- and 8-nitroisoquinolines. Bromination in the presence of aluminium trichloride at 75 °C gives a 78% yield of 5-bromoisoquinoline. 

C-Aminoindoles autoxidize extremely rapidly. Consequently, comparatively few chemical reactions have been examined. The 2-amino derivative exists in the 3H-indole tautomeric form (473) and is protonated and alkylated on the annular nitrogen atom (72HC(25-2)179). The 1-methyl derivative (474) exits predominantly as such and not as the alternative 2-imino-3//-indole tautomer and is protonated at the 3-position to give a cation having the same electronic structure as that of the protonated (473). Acylation of (473) yields l-acetyl-2-acetylaminoindole, via the initial acylation of the annular nitrogen atom. Confirmation of this route has been established by the observation that 2-acetylaminoindole, obtained by hydrolysis of the diacetylated compound, is acetylated under identical conditions... 

Both protonated and alkyl-substituted hydrazido(2—) complexes are readily available from the protonation or alkylation of coordination dinitrogen (equations 163 and 164). 

Protonation or alkylation of aryldiazenido precursors provides a route to aryl-substituted hy-drazido(2—) complexes (equations 165, 166 and 167). Diazenido complexes have been covered in Section 13.3.6. 

Since the efficiency of fluorescence quenching of the sensitizer paralleled the oxidizability of the arene in a series of substituted alkyl benzenes, the reaction was thought to proceed through electron transfer followed by protonation and trapping of the radical by oxygen. 

Rapid development of this area followed the discovery of routes to these complexes, either by ready conversion of terminal alkynes to vinylidene complexes in reactions with manganese, rhenium, and the iron-group metal complexes (11-14) or by protonation or alkylation of some metal Recent work has demonstrated the importance of vinylidene complexes in the metabolism of some chlorinated hydrocarbons (DDT) using iron porphyrin-based enzymes (15). Interconversions of alkyne and vinylidene ligands occur readily on multimetal centers. Several reactions involving organometallic reagents may proceed via intermediate vinylidene complexes. 

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