The first NordCO2 collaboration paper of the year is from UiT and HU, involving PhD students Aleksi (HU), Dat (UiT), and Jere (HU) from Kathrin’s and Timo’s groups. Together, they studied the the synthesis of butyrolactones from CO2 using  titanacyclopropane as mediator.

Graphical abstract: Titanium isopropoxide-mediated cis-selective synthesis of 3,4-substituted butyrolactones from CO2

We report a Ti(OiPr)4-mediated multicomponent reaction, which produces 3,4-substituted cis-δ-lactones from alkyl magnesium chloride, benzaldehyde and CO2. The key intermediate, titanacyclopropane, is formed in situ from Ti(OiPr)4 and a Grignard reagent, which enables 1,2-dinucleophilic reactivity that is used to insert carbon dioxide and an aldehyde. An alternative reaction route is also described where a primary alkene is used to create the titanacyclopropane. A computational analysis of the elementary steps shows that the carbon dioxide and the aldehyde insertion proceeds through an inner-sphere mechanism. A variety of cis-butyrolactones can be synthesized with up to 7 : 1 diastereoselectivity and 77% yield.

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