Intramolecular functionalization

Fig. 4. Synthesis of estrone (20) through elimination of unactivated 19-methyl group via intramolecular functionalization of C-19. -TsOH...

The selectivity observed in most intramolecular functionalizations depends on the preference for a six-membered transition state in the hydrogen-atom abstraction step. Appropriate molecules can be constmcted in which steric or conformational effects dictate a preference for selective abstraction of a hydrogen that is more remote from the reactive radical. 

In this section we focus on intramolecular functionalization. Such reactions normally achieve selectivity on the basis of proximity of the reacting centers. In acyclic molecules, intramolecular functionalization normally involves hydrogen atom abstraction via a six-membered cyclic TS. The net result is introduction of functionality at the S-atom in relation to the radical site. 

There are also useful intramolecular functionalization methods that involve hydrogen atom abstraction by oxygen radicals. The conditions that were originally developed involved thermal or photochemical dissociation of alkoxy derivative of Pb(IV) generated by exchange with Pb(OAc)4.374 These decompose, giving alkoxy... 

Indoles were synthesized by the intramolecular functionalization of a benzylic C-H bond. Hence, the reaction of 2,6-xylyl isocyanide with a ruthenium complex led to 7-methylindole (Equation (36)). 

HDV ribozymes are derived from the genomic and the antigenomic RNAs of hepatitis delta virus [99-102]. Studies by three groups have revolutionized our understanding of the mechanism of HDV ribozyme-catalyzed reactions [28, 103, 104]. They demonstrated recently that an intramolecular functional group, namely N3 at Gye in the antigenomic HDV ribozyme and N3 at C75 in the genomic HDV ribozyme, can, in fact, act as a true catalyst. However,... 

Further preliminary studies of direct auration of furane and thiophene derivatives were performed by Schmidbaur et al., who synthesised several organogold compounds similar to 89 or 90 [71] and the research of He and Shi on the gold(III)-catalyzed inter- or intramolecular functionalization of aromatic —H bonds confirmed the possibility of such processes [21] (Figure 8.2). 

C-H functionalization, 10, 121 C-H intermolecular functionalization, 10, 122 C-H intramolecular functionalization, 10, 130 olefin functionalization, 10, 155 /)3-Carbon atoms, C-H bond functionalization activated alkyl groups intermolecularly, 10, 111 activated alkyl groups intramolecularly, 10, 114 alkanes and alkyl units, 10, 102 Carbon-based ligands, alkali metal chemistry, 2, 3 Carbon-based 77-ligands, in molybdenum carbonyls alkenes, 5, 433 alkynes, 5, 435 allenes, 5, 433... 

INTRAMOLECULAR FUNCTIONALIZATION IN THE ViaNITY OF EXISTING SUBSTRATE FUNCTIONAL GROUPS... 

INTRAMOLECULAR FUNCTIONALIZATIONS IN THE VICINITY OF EXISTING SUBSTRATE FUNCnONAL GROUPS... 

Betancor, C., Concepcion, J. I., Hernandez, R., Salazar, J. A., Suarez, E. Intramolecular functionalization of nonactivated carbons by amidylphosphate radicals. Synthesis of 1,4-epimine compounds. J. Org. Chem. 1983, 48,4430-4432. 

Additions to conjugated systems are further facilitated by some of the features discussed previously e.g., additions to dienes" " and enynes" in the presence of transition-metal catalysts and additions to enynes containing a suitably placed intramolecular function such as hydroxyl. Although uncatalyzed intermolecular additions to alkynylsilanes are not yet demonstrated, additions are seen in the presence of a transition-metal catalysts" and intramolecular additions to alkynylsilane functions by suitably placed internal organomagnesium-halide functions are facile. ... 

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