Reductive CO 2 Homocoupling: Synthesis of a Borylated C 3 Carbohydrate

International audience; To use carbon dioxide as a source of carbon, recent progress has been made toward the synthesis of higher value chemicals and in particular toward Cn compounds. In this context, we report here the synthesis of a borylated C3-carbohydrate from CO2 as the only source of carbon. This result corresponds to the unprecedented formation of a polyol chain and of asymmetric carbon atoms from CO2. The adopted strategy involves the Fe-catalysed selective 4e− reduction of CO2 into bis(boryl)acetal followed in one-pot by a carbene-mediated C−C coupling reaction. Boron is shown to play a key role in the coupling step enabling to observe the first diastereoselective formose-type reaction. This result is in addition obtained under mild reaction conditions (T