Rhodium(II)‐Catalyzed Inter‐ and Intramolecular Enantioselective Cyclopropanations with Alkyl‐Diazo(triorganylsilyl)acetates

<jats:title>Abstract</jats:title><jats:p>The intermolecular cyclopropanation of styrene with ethyl diazo(triethylsilyl)acetate (<jats:bold>1a</jats:bold>) proceeds at room temperature in the presence of chiral Rh<jats:sup>II</jats:sup> carboxylate catalysts derived from imide‐protected amino acids and affords mixtures of <jats:italic>trans</jats:italic>‐ and <jats:italic>cis</jats:italic>‐cyclopropane derivatives <jats:bold>2a</jats:bold> in up to 72% yield but with modest enantioselectivities (<54%) (<jats:italic>Scheme 1</jats:italic> and <jats:italic>Table 1</jats:italic>). Protiodesilylation of a diastereoisomer mixture <jats:bold>2a</jats:bold> with Bu<jats:sub>4</jats:sub>NF is accompanied by epimerization at C(1) (→<jats:bold>3</jats:bold>). The intramolecular cyclopropanation of allyl diazo(triethylsilyl)acetate (<jats:bold>8a</jats:bold>), in turn, affords optically active 3‐oxabicyclo[3.1.0]hexan‐2‐one (<jats:bold>9a</jats:bold>) with yields of up to 85% and 56% ee (<jats:italic>Scheme 3</jats:italic> and <jats:italic>Table 2</jats:italic>). Similarly, the (2<jats:italic>Z</jats:italic>)‐pent‐2‐enyl derivative <jats:bold>8d</jats:bold> reacts to <jats:bold>9d</jats:bold> in up to 77% yield and 38% ee (<jats:italic>Scheme 3</jats:italic> and <jats:italic>Table 3</jats:italic>). In contrast, the diazo decomposition of (2<jats:italic>E</jats:italic>)‐3‐phenylprop‐2‐enyl and 2‐methylprop‐2‐en‐1‐yl diazo(triethyl‐silyl)acetates (<jats:bold>8b</jats:bold> and <jats:bold>8c</jats:bold>, resp.) is unsatisfactory and gives very poor yields of substituted 3‐oxabicyclo[3.1.0]hexan‐2‐ones <jats:bold>9b</jats:bold> and <jats:bold>9c</jats:bold>, respectively (<jats:italic>Table 3</jats:italic>).</jats:p>