Possible Mechanisms and Origin of Selectivities for Phosphine‐Catalyzed [2+n] (n=3, 4) Annulations of Saturated Amines and δ‐Acetoxy Allenoates

Abstract

The density functional theory (DFT) calculations were performed to gain insights into possible reaction mechanisms and origin of selectivities on phosphine catalyzed [2+3] and [2+4] annulations of saturated amine with allenoate for the first time. The computed results reveal that allenoate prefers to serve as a C3 synthon rather than C4 synthon under phosphine catalysis, and the whole catalytic cycle generally undergoes through eight processes, i. e. (1) adsorption of catalyst, (2) dissociation of AcO− group, (3) deprotonation of saturated amine, (4) nucleophilic attack by the deprotonated amine anion to the electrophilic phosphonium diene intermediate, (5) [1,6]‐proton shift, (6) ring closure of five‐membered heterocycle, (7) [1,2]‐proton shift, and (8) desorption of catalyst and the formation of 3‐pyrroline. The fourth step was identified as both chemo‐ and stereo‐selectivities determining step, and the pathway associated with R‐isomer is energetically favorable pathway. Further non‐covalent interaction (NCI) and Bader's atoms‐in‐molecules (AIM) analysis reveal that the C−H⋅⋅⋅O interaction has a significant contribution to the stability of R‐configured transition state. The obtained insights should be valuable for understanding the general principle for the detailed mechanism and predicting the origin of the chemo‐ and stereo‐selectivities on the phosphine catalyzed [2+3] and [2+4] annulations of saturated amine with allenoate.

DFT investigation of the DDQ-catalytic mechanism for constructing C–O bonds

“…24 The structures for reactants, intermediates, transition states and products were calculated at the level of M06-2X-D3/ma-def2-SVP [25][26][27][28][29][30] in the SMD solvent model, 31 which has been proved to be a powerful method to obtain accurate results in the process of investigating the mechanisms of organic chemistry. 4,14,15,[31][32][33][34][35][36][37][38][39][40][41] The vibration analysis shows no imaginary frequency, indicating that the corresponding structure is located at the minimum position on its potential energy surface, and the stability of the optimized compound is established. Intrinsic reaction coordinates (IRCs) have been calculated to make sure that each transition state is correct.…”

“…6,8,[12][13][14] For example, Aleksey Yu and his team catalyzed the coupling reaction between 4-cyanopyridine and fatty tertiary amines to yield α-pyridine-4-tertiary amines using the fac-Ir( ppy) 3 photocatalyst. 15 Despite the mild reaction conditions, the use of transition metals may not align with the principles of "atom and step economies". The second kind consists of non-metallic organic photocatalysts.…”

DFT Investigation for the Mechanisms of γ-Butyrolactones from Styrene and Acrylic Acid, Catalyzed by NMA*BF 4 and PhSSPh

“…All the results are calculated by Gaussian 09 program 36 . The structures including reactants, transition states, intermediates and product were optimized with the level of M06-2X-D3 37 /ma-def2SVP, respectively, which has been proved to be a powerful method to obtain accurate results in the process for investigating the mechanisms of organic chemistry [38][39][40][41][42][43][44][45][46][47][48][49][50][51] . And SMD model 52 was taken to simulate the solvent effect of dichloromethane.…”

Kinetics and mechanism of the Barton–Kellogg olefination: a computational DFT study using CTST theory and topological approaches

“…Phosphines with a lone pair of electrons are powerful Lewis base catalysts which are widely used in the synthesis of organic compounds. 23,24…”