Effect of remote trigonal carbons on the kinetics of Bergman cyclization: synthesis and chemical reactivity of pyridazinedione-based enediynes.
The synthesis and chemical reactivity of pyridazinedione-based enediynes (1, 2) are described. Both of these enediynes, namely the dihydro compound 1 and its corresponding tetrahydro analogue 2, were prepared by double N,O-alkylation of the corresponding heterocyclic system with the acyclic enediynyl dibromide 8 in good yields. Their single-crystal X-ray structures revealed similar c, d distances (distance between the acetylenic carbons undergoing covalent connection in Bergman cyclization). Interestingly, these molecules undergo Bergman cyclization at different rates, and the reactivity is shown to be dependent upon the state of hybridization of C-4 and C-5 atoms of the parent heterocyclic ring.
Basak
Amit
A
Bioorganic Chemistry Laboratory, Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India. absk@chem.iitkgp.ernet.in
Bag
Subhendu Sekhar
SS
Majumder
Pooja Anjali
PA
Das
Amit Kumar
AK
Bertolasi
Valerio
V