Transalkylation and Migration of N‐Substituent upon Alkylation of 1,2,3‐Triazoles Containing Good Leaving N‐Substituents

Abstract

The synthesis of four new 1,2,3‐triazole derivatives and seven 1,2,3‐triazolium salts that contain an organometallic group (i.e., cymantrenyl and ferrocenyl) at either the N‐1, N‐2, or N‐3 position was realized. The alkylation of organometallic and organic triazole derivatives was investigated, and as a result of these studies, it was found that the presence of a good leaving group at the heterocyclic nitrogen atom led to transalkylation and subsequent migration of the N‐1 substituent to the N‐2 position of the triazole moiety. The nucleophilicity of the counterion of the triazolium salt influenced the transalkylation and isomerization processes, which suggests that the elimination of the N‐substituent most likely occurs though a concerted mechanism with nucleophilic assistance from the counterion. Thus, a new approach to the synthesis of 2,4‐disubstituted 1,2,3‐triazoles has been developed.

CO‐Preserving Photoinduced Transfer of Cymantrenyl Moiety: a Tandem Experimental and Computational Investigation

“…This migration can occur via synchronous or dissociative‐associative [46] mechanism (top and 2 nd rows in Scheme 2). We were unable to locate the zwitterionic complex 9 , however transition state (TS) for synchronous transfer ( TS‐3‐4 ) was readily located with activation free energy of 43 kcal/mol.…”

Rearrangements and Migrations along the Ferrocene Periphery: On the Way to Planar‐Chiral and (Multi)Substitution Patterns

“…The formation of stable α‐ferrocenyl carbocations also facilitates C−N bond cleavage and causes FcCH 2 ‐substituted triazoles 177 to rearrange from a 1 H into their 2 H ‐substituted derivatives (Scheme 47). [48] It was initially mentioned that iodide ions act as a catalyst for this reaction and form 179 and 180 as intermediates. However, the reaction also proceeds in the presence of non‐nucleophilic BF 4 − anions, indicating that the FcCH 2 + species rearranges directly, whereby methylation or ferrocenylmethylation towards 178 + or 181 + , respectively, is still required [48] …”

“… [48] It was initially mentioned that iodide ions act as a catalyst for this reaction and form 179 and 180 as intermediates. However, the reaction also proceeds in the presence of non‐nucleophilic BF 4 − anions, indicating that the FcCH 2 + species rearranges directly, whereby methylation or ferrocenylmethylation towards 178 + or 181 + , respectively, is still required [48] …”

“…However, the reaction also proceeds in the presence of non-nucleophilic BF 4 À anions, indicating that the FcCH 2 + species rearranges directly, whereby methylation or ferrocenylmethylation towards 178 + or 181 + , respectively, is still required. [48] In general, α-ferrocenyl carbo cations are known for diverse reactions to act as electrophiles during S E Ar reactions. However, an unexpected rearrangement was recently observed for ortho-P(X)Ph 2 -functionalized ferrocene compounds 182 (X = S, Se) depending on the reaction conditions (Scheme 48).…”

“…Cationic-induced isomerization of ferrocenyl triazole 177 from their 1H into a 2H-form. [48] Scheme 48. Synthesis of thio ethers from ferrocenyl methanols 182 via chalcogene transfer.…”