Preparations of several heterocycles by intramolecular cyclization of the tellurols and related, compounds to a triple bond are described. Reaction of
o-diethynylbenzene with Na
2Te in the presence of NH
2-NH
2 gave 3-benzotellurepine. 1-Benzo-tellurepines and -selenepines were prepared from (
Z) -1- (
o-bromophenyl) but-1-en-3-ynes
via the tellurol and selenol intermediates, respectively. 1-Benzo-thiepines and -stannepines were also obtained by the similar 7-
endo-
dig ring closure reaction. Benzo [
b] tellurophenes and related compounds were synthesized in one pot from
o-bromoethynylbenzene derivatives. Reaction of 2-ethynylbenzoyl chlorides with NaHTe and NaHSe resulted in 5-
exo-
dig ring closure to afford (
Z) -3-methylidene-tellurophthalides and -selenophthalides regio- and stereospecifically, respectively. Treatment of
o-bromophenyl ethynyl ketones with NaHTe and NaHSe gave telluro- and selenochromen-4-ones, respectively, in one pot.
o-Iodopropioanilides reacted with NaHTe to give 1, 5-benzotellurepinones
via the phenyltellurols. Isotelluro- and isoselenochromenes were obtained by reaction of
o-ethynylbenzyl bromides with NaHTe and NaHSe
via the 6-
endo-
dig cyclization of the benzyl tellurols and benzyl selenols together with the corresponding 5-
exo-
dig products, respectively.
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