Scheme 3.
Rhodium catalyzed coupling of acetylene to aldehyde 14a in the absence of hydrogen and Brønsted acid cocatalyst delivers ketone 14b, corroborating intervention of the proposed oxarhodacycloheptadiene intermediate.
Rhodium catalyzed coupling of acetylene to aldehyde 14a in the absence of hydrogen and Brønsted acid cocatalyst delivers ketone 14b, corroborating intervention of the proposed oxarhodacycloheptadiene intermediate.