1,3-Dipolar cycloaddition of diaryldiazomethanes across N-ethoxy-carbonyl-N-(2,2,2-trichloroethylidene)amine and reactivity of the resulting 2-azabutadienes towards thiolates and cyclic amides

Abstract1,3-dipolar cycloaddition of diaryldiazomethanes Ar2CN2 across Cl3C–CHN–CO2Et 1 yields Δ3-1,2,4-triazolines 2. Thermolysis of 2 leads, via transient azomethine ylides 3, to diaryldichloroazabutadienes [Ar(Ar')CN–CHCCl2] 4. Treatment of 4a (Ar = Ar' = C6H5) and 4c (Ar = Ar' = p-ClC6H4) with NaSR in DMF yields 2-azabutadienes [Ar2CN–C(H)C(SR)2] 5. In contrast, nucleophilic attack of NaStBu on 4 affords azadienic dithioethers [Ar2CN–C(StBu)C(H)(StBu)] (7a Ar = C6H5; 7b Ar' = p-ClC6H4). The reaction of 4a with NaSEt conducted in neat EtSH produces [Ph2CN–C(H)(SEt)–CCl2H] 8, which after dehydrochloration by NaOMe and subsequent addition of NaSEt is converted to [Ph2CN–C(SEt)C(H)(SEt)] 7c. Upon the reaction of 4c with NaSiPr, the intermediate dithioether [(p-ClC6H4)2CN–CHC(SiPr)2] 5k is converted to tetrakisthioether [(p-iPrSC6H4)2CN–CHC(SiPr)2] 6. Treatment of 4a with the sodium salt of piperidine leads to [Ph2CN–CHC(NC5H10)2] 10. The coordination of 6 on CuBr affords the macrocyclic dinuclear Cu(I) complex 11. The crystal structures of 5i, 7a,b, 10 and 11 have been determined by X-ray diffraction