Intra-intermolecular reaction

A less efficient mode of the two-alkyne annulation is the intra-intermolecular reaction of an alkyne-containing carbene complex of the type (312) with a second alkyne. Under optimal conditions, these reactions will lead to moderate yields of bicyclic phenols of the type (313), which result from the assembly of pieces indicated by (315). The precursor dienones (314) can be isolated as minor products from these reactions.Applications of the two-alkyne annulations in organic synthesis have not yet been reported. 

Alternative diamination protocols have recently become available. Within this context, Hong and Johnston have developed several intra-/intermolecular reactions, which employ substrates of 2-hydroxy- and 2-amino-substitued styrene derivatives and vinyl pyridines [69-71 ]. The transformation employs a combination of 2 equiv. of PhI(OAc)2, overstoichiometric amounts of Kl, and an additional nitrogen source, and although the reaction mechanism remains to be established fuUy, the prominent participation of the hypervalent iodine reagent is obvious. 

First-order and second-order rate constants have different dimensions and cannot be directly compared, so the following interpretation is made. The ratio intra/ inter has the units mole per liter and is the molar concentration of reagent Y in Eq. (7-72) that would be required for the intermolecular reaction to proceed (under pseudo-first-order conditions) as fast as the intramolecular reaction. This ratio is called the effective molarity (EM) thus EM = An example is the nu-... 

The rhodium-catalyzed tandem carbonyl ylide formation/l,3-dipolar cycloaddition is an exciting new area that has evolved during the past 3 years and high se-lectivities of >90% ee was obtained for both intra- and intermolecular reactions with low loadings of the chiral catalyst. 

Intramolecular reactions usually dominate intermolecular addition for favorable ring sizes. Semiempirical (AMI) calculations found the intramolecular TS favorable to a comparable intermolecular reaction.68 (See Figure 4.1) The intramolecular TS, which is nearly 4 kcal/mol more stable, is quite productlike with a C—O bond distance of 1.6 A, and a bond order of 0.62. The bromonium ion bridging is unsymmetrical and fairly weak. The bond parameters for the intra- and intermolecular TSs are quite similar. 

Thermally induced intra-intermolecular criss-cross cycloaddition of nonsymmetrical azines 363 in the presence of phenyl isocyanate provides the corresponding products of the mixed criss-cross cycloaddition 364 (Scheme 55) <2002TL6431>. Two different reaction mechanisms, intra-intermolecular and inter-intramolecular, of the mixed criss-cross cycloaddition with opposite sequence of reaction steps are possible. Quantum chemistry calculations suggest the intra-intermolecular mechanism as the most probable mechanism of this reaction <2004CCC231>. 

The importance of intramolecular cyclization was emphasized when Butler and coworkers found that the radical polymerization of N, N, N, /V-diallyldimethylammonium chloride (DADMAC) gave soluble, uncrosslinked polymers with little or no unsaturation (Eq. 6-101) [Butler and Angelo, 1957 Butler and Ingley, 1951 Wandrey et al., 1999]. There is a very low tendency for radical IV to propagate intermolecularly and undergo crosslinking. The predominant reaction is intramolecular cyclization, and the product is a linear product with cyclic structures in the backbone. The reaction is referred to as alternating intra/intermolecular polymerization or cyclopolymerization. 

Because reactive intermediates (RIs) undergo facile intra- and/or intermolecular reactions, they are, by definition, short lived. As described in the other chapters in this volume, the transient namre of RIs provides a challenge to their direct spectroscopic observation. When the spectra of a putative RI can be obtained, it may not be certain that the observed spectra actually belong to the RI. 

The main steps in the currently accepted catalytic cycle of the Heck reaction are oxidative addition, carbopalla-dation (G=G insertion), and / -hydride elimination. It is well established that both, the insertion as well as the elimination step, are m-stereospecific. Only in some cases has formal /r/ / i--elimination been observed. For example, exposure of the l,3-dibromo-4-(dihydronaphthyloxy)benzene derivative 16 and an alkene 1-R to a palladium source in the presence of a base led to a sequential intra-intermolecular twofold Heck reaction furnishing the alkenylated tetracyclic products 17 in good to excellent yields (Scheme 9). " In the rate-determining step, the base removes a proton in an antiperiplanar orientation from the benzylic palladium intermediate. The best amine base was found to be l,4-diazabicyclo[2.2.2]octane, which apparently has an optimal shape for this proton abstraction. 

Scheme 9 Sequential intra-intermolecular twofold Heck reaction involving a trans-/ -hydride elimination. ...

Grigg and Xu have developed a variety of so-called queuing cascades involving allenes. The intra-intermolecular carbopalladation sequence of the <9-iodo-A-methyl-A -(methylallyl)aniline 142 and 1,1-dimethylallene 143 with subsequent / -dehydropalladation leads to the 1,3-dienyl-substituted indole derivative 144, which is immediately trapped by an added dienophile (e.g., A-methylmaleimide) in a Diels-Alder reaction to yield 145 (Scheme 37)7 ... 

The pyrolytic reactions of pentafluorophenyl and heptafluoro-2-naphthyl propargyl ethers give product mixtures containing benzo- and naphtho[6]furan derivatives, resulting from initial Claisen rearrangement followed by further intra- and intermolecular reactions.31 34... 

The presence of defects caused by incomplete reaction in the particles has been found while comparing intra- and intermolecular reaction rates in polycomplexes obtained by mixing polymer solutions, and by matrix polymerization 461. In the latter case a polycomplex is formed simultaneously with the chain growth which is connected with the complementary macromolecule, the matrix. This process of polycomplex formation is closer to the equilibrium one — in any case there are considerably fewer obstacles here for forming an uninterrupted sequence of intermolecular bonds. That is why the rate and conversion of thermochemical reactions (which are connected with the presence or absence of defects — loops or tension in double-stranded chains of the polycomplex) depend on how the polycomplex have been obtained. After its destruction and reconstruction (e.g., by increasing and then decreasing of pH in the case of p.c. (PMA — PVPD)) the matrix polycomplex does not differ from the one obtained by mixing 46). 

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