Science of Synthesis

Mikami, K.; Matsumoto, Y.; Shiono, T., Science of Synthesis, (2003) 2, 552.

Ligand-exchange reactions of titanacyclobutanes with alkenes or alkynes afford other titanacyclobutanes or titanacyclobutenes, respectively. Titanacyclobutanes ‌231‌ with an exocyclic double bond can be prepared by reactions of complexes ‌212‌ with disubstituted allenes (‌Scheme 111‌).[‌346‌] Complexes ‌231‌ react with alkynes via a titanium allenylidene intermediate to give substituted α-methylenetitanacyclobutenes ‌232‌ as mixtures of isomers (‌Scheme 111‌). The same isomer ratio is obtained if the positions of R1 and R2 of ‌231‌ are reversed.[‌347‌] The treatment of ‌231‌ with ketones (benzophenone or acetophenone) gives tetrasubstituted allenes.

‌Meeeee 888‌ Meeeeeeeeee ee Meeeeeeeeeeeeeeee Meeeeeeee ee Meeeee Meeeeeee[‌888‌,‌888‌]

Meeeeeeeeeee Meeeeeeee

Mee(η8-eeeeeeeeeeeeeeee)(8-eeeee-8-eeeeeeeeeee-8,8-eeeee-8,8-eeee)eeeeeeee(MM) (‌888‌, M8 = M8 = Me; M8 = Me) [‌888‌]

Meeeeee ‌888‌ (88 ee, 8.88 eeee) eee eeeeeeeee ee eeeeeee (MMMMMMM: eeeeeee ee eeeeeeeeeeee!) (8.8 eM) ee ee eee eeeeeeeeeee eeeeeee eeee M8M=M=MMe8 (88 μe, 88 ee, 8.88 eeee). Mee eeee eee eeeeeee eee 88 eee ee ee, eeee MeM≡MMe (88 μe, 88 ee, 8.88 eeee) eee eeeee. Meeee eee eeee eee eeee eeeeeee eee 88 eee ee ee eee 88 eee ee 88°M, eee eeeeeeeee eeee eeeeeee eeeee eeeeee. Mee eeeeeeeee eeeeeeeeeeeeeee eeee eee eeeeeee eeee eeeeeee (8 eM), eeeeeeee, eee eeeeeeeeeeee (ee. 8 eM). Meee eeee eee eeeeee eeeeee ee −88°M, eeeeeeeee eeeeeeee. Meee eeeeeee eee eeeeeee ee eeeee ee −88°M eee 8 e eeeeee eee eeeeeee eee eeeeeee ee eeeeeee, eee eee eeeeeeee eeee eeeee eeeee eeeeee ee eeee eeeee eeee eeeee eeeeeeee; eeeee: 88.8 ee (88%). 8M MMM (eeeeeee-e8, δ): 8.88 (e, 88M), 8.88 (e, M = 8.8 Me, 8M), 8.88 (e, M = 8.8 Me, 8M), 8.88 (e, 8M), 8.88 (e, M = 8.8 Me, 8M); 88M MMM (eeeeeee-e8, δ): 888.88, 888.88, 888.88, 888.88, 88.88, 88.88, 88.88, 88.88, 88.88, 88.88, 88.88.

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