Methyl ethyl-cyclopentane products

Concurrently, Noels had reported that rhodium carboxylates smoothly catalyze the intermolecular C—H insertion of ethyl diazoacetate into alkanes. Following up on this report, Taber demonstrated that the open chain a-diazo 3-keto ester (60) cyclizes smoothly under rhodium acetate catalysis to give the corresponding cyclopentane (61 equation 24). In contrast to the copper-mediated cyclization cited above (equation 22), the six-membered ring product is not observed. The insertion shows significant electronic selectivity. Although there is a 3 1 statistical preference for methyl C—H, only the methylene C—H insertion product (61) is observed (equation 24). 

---