A versatile synthesis of 1-benzoheteroepines containing group 14, 15, and 16 heavier elements via a common 1,6-dilithium intermediate

Article abstract of DOI:10.1248/cpb.47.1108

Fully unsaturated group 14 (Si, Ge, and Sn), group 15 (P, As, Sb, and Bi) and group 16 (S, Se, and Te) 2-trimethylsilyl-1-benzoheteroepines (16a- j), including the first isolated examples of bismepines, have been prepared by reaction of the corresponding electrophilic metal reagents (MX₂ or MX₄; M=group 14, 15, and 16 heavier elements) with the key 1,6-dilithium intermediate (9), generated from the common starting compound (Z,Z)-1-bromo- 4-(2-bromophenyl)-1-trimethylsilyl-1,3-butadiene (14) by treatment with tert- butyllithium. The trimethylsilyl group in 16b-j was readily removed by treatment with tetrabutylammonium fluoride to give the desired C- unsubstituted 1-benzoheteroepines (1b-j). Single crystal X-ray analyses of 1d (P) and 1f (Sb) revealed that the seven-membered rings exist in boat conformations with the heteroatoms at the bows. All obtained C-unsubstituted group 15 and 16 1-benzoheteroepines (1d-j) were thermolabile in solution towards heteroatom extrusion, while heteroepines (16d-j) having the bulky trimethylsilyl group at the 2-position were much more stable than 1d-j. The half-lives of 1d-j estimated from ¹H-NMR spectral analysis indicate that the thermal stabilities of 1d-j decrease in the order 1f (Sb)>1d (P)>1e (As)>1g (Bi) in the group 15 heteroepines and 1j (Te)>1i (Se)>1h (S) in the group 16 heteroepines.

Full text of DOI:10.1248/cpb.47.1108

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