Several α-diazo β-keto nitriles bearing trans-2-allyl-, -vinyl-, or -phenylcycloalkyl groups were prepared and their intramolecular cyclopropanation reactions were examined. In the presence of Rh2(OAc)4 (1 mol%) as a catalyst, the allyl- and vinyl-substituted precursors were found to undergo cyclopropanation smoothly at ambient temperature to afford novel tricyclic α-keto cyclopropyl nitriles in 47–88% yields with diastereomeric ratios ranging from 79:21 to >99:1. On the other hand, the catalytic reactions of the phenyl-containing analogues did not give any cyclopropyl products, but instead provided functionalized hexa­hydrophenanthrene or tetrahydrocyclopentanaphthalene derivatives in quantitative yields.

Under the catalysis of Cu(OTf)2 in refluxing CH2Cl2, ethyl α‐dizao α‐(diethylphosphoryl)acetate was shown to undergo a new cyclization reaction to afford a pentacovalent oxaphosphirane product. The reaction is proposed to occur through the addition of the P=O double bond to the copper carbenoid, followed by the hydrolysis of the ylide intermediate. Our finding represents the first example on producing oxaphosphiranes from dizao phosphoryl compounds. On the other hand, the corresponding rhodium carbenoid displayed the different reactivity under the same thermal conditions, to produce the β‐propiolactone through the well‐recognized C‐H insertion pathway.

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