Low-valent dialkoxytitanium(ii): a useful tool for the synthesis of functionalized seven-membered ring compounds

Abstract

Herein, we describe an unprecedented access to all-carbon or heterocyclic seven-membered ring frameworks from 1,8-ene-ynes promoted by inexpensive low-valent titanium(II) species, readily available from Ti(OiPr)4 and Grignard reagent. A broad...

Low-valent titanium(ii) mediated intramolecular and regioselective alkyne/alkoxyallene reductive coupling reactions

“…In line with our previous works, 13 we investigated the formation of seven-membered ring frameworks. Reaction Conditions A were thus applied to the precursor 43 , affording a mixture of the desired seven-membered ring 44 and the reduced product 45 which could not be separated (respectively 23 and 17% 1 H NMR yield) (Scheme 5).…”

“…In order to push forward the conversion of the titanacyclopropene intermediate into cyclized adducts, and considering that seven-membered ring synthesis requires higher temperature than that of five- and six-membered rings, the reaction was performed at room temperature. 13,17 Both products 44 and 45 were observed as traces. However, a new seven-membered ring 46 was obtained as the major product of the reaction in 23% yield along with degradation.…”

“…The cyclization precursor 1 was prepared in five steps with good overall yield. 12 At first, the application of reaction conditions inspired from our previous works 13 led to a complex mixture. However, it was possible to observe the desired compound 2 as traces.…”