A general and stereoselective approach to 14-membered cyclic bis-semicarbazones involving BF₃-catalyzed amidoalkylation of 2-(trimethylsilyloxy)propene

Abstract

A general and stereoselective five-step approach to 14-membered cyclic bis-semicarbazones, 5,12-diaryl-7,14-dimethyl-1,2,4,8,9,11-hexaazacyclotetradeca-7,14-diene-3,10-diones, starting from aldehyde semicarbazones has been developed. The key intermediates, 4-(3-oxobut-1-yl)semicarbazones, were prepared by BF3-catalyzed amidoalkylation of 2-(trimethylsilyloxy)propene with...

Density Functional Theory Study on Ring-Chain Isomerism of Semicarbazones

“…Proc. 2023, 14, 13 2 of 6 semicarbazones [14,15], we initiated a research program aiming to study the isomerization of semicarbazones into 1,2,4-triazolidin-3-ones.…”

“…semicarbazones/1,2,4-triazolidin-3-ones interconversion remains a challenge for synthetic and theoretical chemistry. As a continuation of our interest in ring-chain isomerism [13] and the synthesis of polyaza compounds based on semicarbazones [14,15], we initiated a research program aiming to study the isomerization of semicarbazones into 1,2,4-triazolidin-3-ones.…”

Unprecedented synthesis of a 14-membered hexaazamacrocycle

“…Nevertheless, the synthesis of novel PAMs with interesting properties is of great importance. Recently, we developed some approaches to 14-membered cyclic bis-semicarbazones [32][33][34][35] and bis-thiosemicarbazone [36], namely 7,14-dimethyl-1,2,4,8,9,11-hexaazacyclotetradeca-7,14-diene-3,10-diones and -3,10-dithiones. The prepared com- pounds were able to chelate various metal cations through the N1, N4, N8, and N11 atoms [37,38].…”

Different Modes of Acid-Promoted Cyclooligomerization of 4-(4-Thiosemicarbazido)butan-2-one Hydrazone: 14-Membered versus 28-Membered Polyazamacrocycle Formation

“…Recently, we discovered unprecedented self-assembly of novel 14-membered cyclic bis-semicarbazones, 1,2,4,8,9,11-hexaazacyclotetradeca-7,14-diene-3,10-diones 3 , upon acid-promoted dimerization of hydrazones of 4-(1-aryl-3-oxobut-1-yl)­semicarbazides 1 (Scheme A) prepared in 4 steps from ethyl carbamate or from semicarbazones of aromatic aldehydes . It is noteworthy that, under similar conditions, close analogues of 1 , hydrazones of 4-(1,3-diaryl-3-oxoprop-1-yl)­semicarbazides 2 , gave only 7-membered cyclic semicarbazones 4 , which indicates a dramatic influence of the substrate structure on the outcome of cyclization.…”

“… 16 Compared with other described 14-membered 1,2,4,8,9,11-hexaazamacrocycles, 13 compounds 3 are conformationally more flexible, providing a rather dynamic binding cavity. However, these ligands have some drawbacks such as their extremely low solubility in common solvents 15 and rather limited possibilities for their modifications to change metal binding properties. To date, only N2,N9-dibutylated derivatives of two macrocycles 3 were prepared.…”