Late-metal metallacyclobutenes have been proposed as intermediates in numerous metal-mediated reactions of alkynes. Here we describe the synthesis of racemic cobaltacyclobutene complexes from cobalt-alkyne complexes, CpCo(PPh3)(η2-RC≡CR1), and ethyl diazoacetate. When R = TMS and R1 = SO2Ph or R = COCF3 and R1 = Ph, the cobaltacyclobutene products (1-PPh3 and 2) are isolated as a single diastereomer. However, when R = TMS and R1 = CO2Et two regioisomeric cobaltacyclobutnenes (3 and 4) are formed. Photolysis of metallacycles 1-L (L = PPh3, PMe3, P(OMe)3) leads to mixtures of diastereomers 1-L and 1-L-diast. Experimental and computational studies address the photo-epimerization mechanism.

Synthesis, structure, and reactivity studies on late-metal metallacyclobutene complexes

256th National Meeting (2018)

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