Synthesis of exo-Imidazolidin-2-one Dienes, Their Isomerization, and Selectivity in Diels–Alder Cycloadditions

Abstract

An efficient and alternative synthesis of exo-imidazolidin-2-one dienes is described. A condensation reaction was carried out with bis-imino derivatives, diacetyl, and triphosgene, affording symmetrically N, N-disubstituted dienes. The use of alkyl methyl α-diketones led to the formation of nonsymmetrical dienes, which underwent isomerization to provide more stable inner-outer-ring dienes under Lewis acid conditions. Evaluation was made of the reactivity as well as regio- and stereoselectivity of these dienes in Diels-Alder reactions. They proved to be highly reactive and selective. DFT calculations of the transition states accounted for their behavior.

Highly selective Diels–Alder and Heck arylation reactions in a divergent synthesis of isoindolo- and pyrrolo-fused polycyclic indoles from 2-formylpyrrole

“…Firstly, the geometry and energy of the TSs and the associated minima along the reaction coordinates of the N-substituted diene 8g with maleimide 7c were calculated at the M06-2X/6-31+G(d,p) level of theory [48][49][50][51] on the Gaussian 09 program [52]. For each stationary point of the Diels-Alder cycloadditions, the relative energy is summarized in Table 6 and the geometry is displayed in Figure 3.…”

Regioselective Mercury(I)/Palladium(II)-Catalyzed Single-Step Approach for the Synthesis of Imines and 2-Substituted Indoles

“…Our group has an ongoing interest in designing and carrying out the novel synthesis of heterocycles [ 69 , 70 , 71 ], and in particular of aza-heterocycles and indoles [ 72 , 73 , 74 , 75 ]. Accordingly, the aim of the present study was to assess the feasibility of preparing indoles in a one-pot process, involving the regioselective Hg(I)-catalyzed hydroamination of terminal alkynes to produce imines as intermediates, and their subsequent Pd(II)-catalyzed cross-coupling oxidative cyclization to afford the corresponding C-2-substituted indoles ( Scheme 1 c).…”

Experimental and Theoretical Approaches in the Study of Phenanthroline‐Tetrahydroquinolines for Alzheimer's Disease

“…However, the cycloaddition reaction [4+2], termed the imino‐Diels‐Alder (iDA), has been one of the most powerful strategies used in synthetic organic chemistry for the construction of these heterocycles . This reaction takes place between Schiff bases represented by imines that can react either as dienes or azadienes and almost always require a Lewis acid (LA) catalyst (Scheme ) ,. Elucidating the molecular reaction mechanism by which the iDA reaction happens has been a topic of growing interest.…”

“…Early evidence presented in the mid‐90s exhibited the presence of type‐THQs zwitterionic intermediaries between N ‐arylimines and dihydrofuran (DHF) under LA‐catalyzed iDA . Nevertheless, very few theoretical studies exist for understanding the reaction mechanisms involving iDA cycloaddition , . Cossio et al .…”

“…[22] Nevertheless, very few theoretical studies exist for understanding the reaction mechanisms involving iDA cycloaddition. [21,23] Cossio et al [24] presented a study of the reaction mechanism between N- (3-pyridyl) aldimines and styrene cyclopentadiene or indene using the BF 3 · Et 2 O catalyst. Results suggested the formation of products arranged in an asynchronous process via the endo transition state, which is favored by the LA.…”