Site- and Regioselectivity of Nitrile Oxide–Allene Cycloadditions: DFT-Based Semiquantitative Predictions

Abstract

Nitrile oxide 1,3-dipolar cycloaddition to arylsulfonyl- and dialkylaminoallenes have been investigated within the framework of the Kohn-Sham density functional theory (DFT) at the B3LYP/6-31G(d,p) level. The hitherto-unexplained experimental behavior of sulfonylallenes was rationalized by transition-state calculations which enabled a semiquantitative treatment of the cycloaddition site- and regioselectivity. The reliability of DFT computations was further established by predicting the complete selectivity of the nitrile oxide cycloaddition to dialkylaminoallenes according to previous experimental findings.

The Azide-Allene Dipolar Cycloaddition: Is DFT Able to Predict Site- and Regio-Selectivity?

“…B3LYP/ 6-31G(d,p) calculations of the reactions between N-heterocyclic carbene-derived C-C-S 1,3-dipoles and 4-benzyl-1-methoxycarbonylallene indicated the major isomer in agreement with experiment [21]. B3LYP/6-31G(d,p) calculations of the cycloaddition between arylnitrileoxides and arylallenes reproduced the site-and regioselectivity of these reactions with semiquantitative accuracy (less than 10% error in both cases) [22].…”

Mechanistic DFT Study of 1,3-Dipolar Cycloadditions of Azides with Guanidine

“…The theoretical study of the reaction mechanism of the 1,3-dipolar cycload azide to the guanidine C=N double bond was initiated w SMD(chloroform)//B3LYP/6-311+G(2d,p) calculations of unsubstituted derivativ AZ1 (hydrazoic acid) and guanidine GU (Figure 2). The B3LYP functional [2 previously used for successful regioselectivity investigations of similar uncatalyzed 1,3-dipolar cycloadditions [22][23][24][25], including azide cycloadd acetylenes [26]; and azide cycloaddition to nitriles forming tetrazoles [27], which applications of DFT methods to this kind of reaction. The theoretical study of the reaction mechanism of the 1,3-dipolar cycloaddition of azide to the guanidine C=N double bond was initiated with the SMD(chloroform)//B3LYP/6-311+G(2d,p) calculations of unsubstituted derivatives: azide AZ1 (hydrazoic acid) and guanidine GU (Figure 2).…”

“…The theoretical study of the reaction mechanism of the 1,3-dipolar cycloaddition of azide to the guanidine C=N double bond was initiated with the SMD(chloroform)//B3LYP/6-311+G(2d,p) calculations of unsubstituted derivatives: azide AZ1 (hydrazoic acid) and guanidine GU (Figure 2). The B3LYP functional [20,21] was previously used for successful regioselectivity investigations of similar thermal, uncatalyzed 1,3-dipolar cycloadditions [22][23][24][25], including azide cycloaddition to acetylenes [26]; and azide cycloaddition to nitriles forming tetrazoles [27], which are early applications of DFT methods to this kind of reaction.…”