Dzhemilev reaction for the synthesis of spiro[3.3]heptane and spiro[3.4]octanes
For the first time cycloalumination of methylenecyclobutane with the aid of Et3Al in the presence of Cp2ZrCl2 leading to 6-ethyl-6-aluminaspiro[3.4]octane has been realized. The latter, without isolation, was converted into spiro[3.3]heptane, 6-thiaspiro[3.4]octane and also spiro[3.4]octan-6-ol and 6-spiro[3.4]octyl formate with high yields and selectivity.
D'yakonov, Vladimir A.,Finkelshtein, Evgeniy Sh.,Ibragimov, Askhat G.
Spiroheptan-3-yl radicals were generated by bromine abstraction from 3-bromospiroheptane and observed by e.s.r. spectroscopy.Both spiroheptane-3-yl and spiroheptan-2-yl radicals were observed on hydrogen abstraction from from spiroheptane.The measured proportions of the two radicals indicated that hydrogen abstraction occurs at roughly the same rate from both C(2) and C(3).The e.s.r. parameters of both radicals show that they are structurally very similar to cyclobutyl radicals.The spiroheptan-2-yl radical rearranges to the cyclobutenylpropyl radical at temperature above ca. 290 K.The photochemical reactions of spiroheptane with bromotrichloromethane and bromine were investigated.Spiroheptylmethyl radicals were generated from the corresponding bromo compound; their rearrangement to 1-allylcyclobutylmethyl radicals was monitored by e.s.r. spectroscopy.Indirect evidence suggested a further rearrangement of 1-allylcyclobutylmethyl radicals to 4-methylenehept-6-enyl radicals.From the activation energy for β-scission in spiroheptylmethyl radicals it was possible to show that the ring strain in spiroheptane cannot exceed twice the ring strain in cyclobutane by more than ca. 3 kcal mol-1.
Roberts, Charles,Walton, John C.,Maillard, Bernard