Heteroatom reaction

The hydrogen transfer (from carbon to the heteroatom). Reactions of the earbon radical. 

C. Heterovinylene Sets with Heteroatom Reaction Sites.137... 

In conformity with our previous approach, we classify substituent effects on heterocyclopropane rings into four categories. They are substituted heterocyclopropyl sets, heterocyclopropylidene sets, heterocyclopropylene sets and hetero-cyclopropanes with heteroatom reaction sites. 

CENTRAL RING CONTAINING ONE HETEROATOM Reaction of 2-bromobenzoic acid (1) with chloroSulfonic acid proceeds to afford the sulfonyl chloride 2 treatment with dimethylamine leads to the corresponding sulfonamide (3). Condensation of bromoacid 3 with the anion from thiophenol in the presence of copper powder results in displacement of halogen by sulfur... 

Some of the ring expansion reactions discussed in Section 2.03.3.3.1 can be extended to five-membered heterocycles containing two or more heteroatoms. Reaction of imidazoles and pyrazoles with dichlorocarbene, for example, gives chloropyrimidines together with small amounts of chloro-pyrazines or -pyridazines, and oxidative ring expansion of 1-aminopyrazole with nickel peroxide gives 1,2,3-triazine (this, in fact, constitutes the only known synthesis of the unsubstituted triazine). There are, however, a number of interesting and useful transformations which are unique to five-membered polyheteroatom systems. 

It is abundantly clear from the preceding discussion that dihalocyclopropanes are versatile intermediates in organic synthesis. Although a wealth of chemistry has already been uncovered, prospects remain bright for interesting developments in the future. Areas such as the application of dihalocyclopropanes in heterocyclic synthesis via carbene insertion into C—H bonds adjacent to heteroatoms, reactions of dihalocyclopropanes with organometallics and the synthetic applications of metallated derivatives deserve further exploration. The chemistry of difluoro-, diiodo- and mixed dihalo-cyclopropanes can be expected to attract some attention. Finally, other heteroatom-substituted cyclopropanes derived ftom dihalocyclopropanes will also invoke further investigation. 

AH the data from the literature were reported at B3LYP/6-311+G. ASEa and ISE are given in kcal mol-1 NICS(O) and NICS(l) in ppm. AA is the exaltation of the magnetic susceptibility aIn the case of having a single heteroatom, reaction 8 is properly balanced. For details see [59, 64]... 

Reactions with Alkali Metals and Other Heteroatom Reactions... 

The nucleophilic site of heterocyclic monomer is a heteroatom. Reaction of heterocycle with a cation (e.g., initiation) leads to onium ion. 

Metal mediated carbometallation of alkynes and alkenes containing adjacent heteroatoms (reactions are accompanied by heterocyclization) 01T5899. 

Phosphorus and arsenic atoms have been introduced into monocyclic rings by the substitution of oxonium groups and tetraalkyltin (Scheme 12). However, this type of reaction does not appear to have been explored for bridgehead situations. Since many of the methods available are reliant on the presence of additional heteroatoms, reactions which substitute these atoms for carbon groups could be useful. Thus the central phosphorus atom of the dithiadiphosphine (57 Z = P) reacts with acetyl chloride and aluminum chloride to produce the phosphine (57 Z = CHMe). 

Pulse radiolysis shows that the pyrimidine radical cations are fairly strong acids and rapidly deprotonate at a heteroatom [reaction (98)]. As protonation/deprotonation reactions at heteroatoms are easily reversible, the radical cations are regenerated upon reprotonation. Deprotonation at carbon or reaction with water yields the final free-radical products [reactions (99) - (101)]. It is noted that in thymidine [23] and 5 -thymidylic acid [104] the allylic thymine radical is observed by EPR and there is very little question that its precursor is the thymine radical cation. The identification of the C(6)-OH-5-yl radical by EPR supports the view [100] that reaction with water competes with the deprotonation at methyl. Due to the ready oxidation of the (reducing) C(5)-OH-6-yl by peroxodisulfate, this type of radical is only observed at low peroxodisulfate concentrations in these systems, i.e. the (oxidizing) C(6)-OH-5-yl radicals are correspondingly enriched under conditions favourable to a chain reaction [22]. In the case of 1,3-dimethyluracil the interesting characteristics of... 

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