Synthesis and Characterization of 22‐, 28‐ and 32‐Membered Mercuraazamacrocycles: Isolation of Ring‐Chain Tautomer and Se/Te‐Containing Macrocycles

Metal‐free synthesis of [Hg‐{1‐C 6 H 4 ‐2‐(imidazolidine)}{1′‐C 6 H 4 ‐2′(‐CHN‐CH 2 )}] 2 ( 8a ) was achieved by (2+2) cyclocondensation of bis(2‐formylphenyl)mercury(II) ( 6 ) with diethylenetriamine. The macrocycle exists as a mixture of tautomers 8a and [Hg‐{1,1′‐(C 6 H 4 ) 2 ‐2,2′‐(CHN)} 2 ‐C 2 H 4 NHC 2 H 4 ] 2 ( 8b ). The cyclization was facilitated by Hg ··· N intermolecular interaction. DFT calculations of tautomers favor the formation of the ring tautomer 8a over the chain tautomer 8b by 18 kcal mol –1 . The reduction of a mixture 8a and 8b with sodium borohydride gave a mixture of 28‐membered reduced mercuraazamacrocycle [Hg‐{1,1′‐(C 6 H 4 ) 2 ‐2,2′‐(CH 2 NH)} 2 ‐C 2 H 4 NHC 2 H 4 ] 2 ( 12 ) and 8a . Macrocycle [Hg‐{1,1′‐C 6 H‐2,3,4‐(OCH 3 ) 3 ‐6,6′‐(CHN)} 2 ‐C 2 H 4 NHC 2 H 4 ] 2 ( 9 ) was synthesized by (2+2) dipodal condensation of bis(6‐formyl‐{2,3,4‐trimethoxy}phenyl)mercury(II) ( 7 ) with diethylenetriamine to obtain the 28‐membered chain tautomer of macrocycle 9 . Reaction of 7 with diethylenetriamine did not give the ring tautomer. 32‐Membered selenium‐ and tellurium‐containing Schiff base macrocycles [Hg‐{1,1′‐C 6 H‐2,3,4‐(OCH 3 ) 3 ‐6,6′‐(CHN)} 2 ‐ C 3 H 6 SeC 3 H 6 ] 2 ( 10 ), [Hg‐{1,1′‐C 6 H‐2,3,4‐(OCH 3 ) 3 ‐6,6′‐(CHN)} 2 ‐C 3 H 6 TeC 3 H 6 ] 2 ( 11 ), and mercuraazametallocryptand [Hg‐{1,1′‐C 6 H‐2,3,4‐(OCH 3 ) 3 ‐6,6′‐(CHN)} 2 ‐{N(C 2 H 4 ) 3 }] 2 ( 12 ) were obtained by (2+2) condensation of bis(6‐formyl‐{2,3,4‐trimethoxy}phenyl)mercury(II) ( 7 ) with 3,3′‐selenobis/telluorobis‐1‐propanamine and tris(2‐aminoethyl)amine respectively.