Intramolecular reaction

About: Intramolecular reaction is a research topic. Over the lifetime, 5015 publications have been published within this topic receiving 138213 citations.

Intramolecular Diels–Alder Reactions

Abstract: The Diels–Alder reaction, first described in 1928,1 has enjoyed widespread use in organic synthesis.2 This [4 + 2] cycloaddition is particularly valuable in that it forms two bonds in a cyclohexenyl system with simultaneous creation of up to four new stereocenters. Curiously, the intramolecular version in which the diene and dienophile are tethered by a connecting chain was not investigated for many years. Alder and Schumaker reported the first example of the intramolecular reaction in 1953,3 but it was not until the early 1960s that additional examples began to appear in the literature.4 Since the mid-1970s, however, a virtual explosion of interest in this reaction has occurred.5 The increased reactivity (due to favorable entropy considerations) and heightened regioselectivity (due to constraints posed by the connecting chain), as well as the potential for the synthesis of stereochemically complex polycyclic ring systems, account for the growth of applications of this reaction in organic and particularly natural products synthesis.

Intramolecular π-Stacking Interaction in a Rigid Molecular Hinge Substituted with 1-(Pyrenylethynyl) Units‡

Abstract: Synthesis of a tetrakis(1-pyrenylethynyl)-substituted rigid hinge-like molecule (1) is described. The intramolecular π-stacking interaction of the pyrene units is studied by 1H NMR and fluorescence spectroscopy. Due to intramolecular π-stacking interactions, chemical shifts of the pyrene protons in 1 are highly shielded in the NMR spectrum. Fluorescence from the static excimer state is observed due to π-stacking interactions among the pyrene units in the ground state of 1. Based on the spectroscopic evidence, conformations and dynamics of 1, arising from the hindered rotation of the major axis, are proposed.

Silicon-initiated carbonylative carbotricyclization and [2+2+2+1] cycloaddition of enediynes catalyzed by rhodium complexes

Abstract: The reaction of dodec-11-ene-1,6-diynes or their heteroatom congeners with a hydrosilane catalyzed by Rh(acac)(CO)2 at ambient temperature and pressure of CO gives the corresponding fused 5-7-5 tricyclic products, 5-oxo-1,3a,4,5,7,9-hexahydro-3H-cyclopenta[e]azulenes or their heteroatom congeners, in excellent yields through a unique silicon-initiated cascade carbonylative carbotricyclization (CO-SiCaT) process. It has also been found that the 5-7-5 fused tricyclic products can be obtained from the same type of enediynes and CO through a novel intramolecular [2+2+2+1] cycloaddition process. The characteristics of these two tricyclization processes and the fundamental differences in their reaction mechanisms are discussed. This novel higher-order cycloaddition reaction has also been successfully applied to the tricyclization of undeca-5,10-diyn-1-als, affording the corresponding 5-7-5 fused-ring products bearing a seven-membered lactone moiety. Related [2+2+2] tricyclizations of enediyne and diynal substrates are also discussed. These newly discovered reactions can construct multiple bonds all at once, converting linear starting materials to polycyclic compounds in a single step. Thus, these new processes provide innovative routes to functionalized polycyclic compounds that are useful for the syntheses of natural and unnatural products.

Palladium-catalyzed [3+2] intramolecular cycloaddition of alk-5-ynylidenecyclopropanes: a rapid, practical approach to bicyclo[3.3.0]octenes.

Abstract: Readily accessible hex-5-ynylidenecyclopropane derivatives cycloisomerize to bicyclic five-membered carbocycles upon heating with catalytic amounts of a palladium complex.