Among carbon-carbon bond-forming processes the 1,2-addition of metal organyl compounds to carbonyl moieties is one of the major reactions in organic synthesis. In the last decade methods based on transition-metal catalysis have been developed that allow stereoselective reactions with a broad spectrum of aldehydes.[1] However, ketones and especially enones still are problematic substrates for which only few catalyst systems are suitable.[2] In contrast, asymmetric 1,4-additions of a variety of organometallic compounds to enones by copper, palladium, and rhodium catalysis are well-established.[3] During our studies towards the total synthesis of the natural product spirodionic acid [4] we envisaged such Rhcatalyzed enantioselective Michael additions to cyclic enones, yet employing aluminum organyl compounds, which-to the best of our knowledge-have hitherto not been used in combination with Rh catalysts. [5] Cyclohex-2-enone (2) was treated with [{Rh(cod)Cl} 2 ] (cod = cyclooctadiene) and an equimolar amount of AlMe 3 to give the desired 3-methylcyclohexanone (1, Scheme 1). To perform the transformation enantioselectively, in situ prepared [{Rh[(S)-binap]Cl} 2 ] was used next; yet the use of this complex led to a dramatic change of the reaction course. Highly selective 1,2-addition was observed and 1-methylcyclohex-2-enol (3) was formed with 96 % ee. Since this compound is a known aggregation pheromone of the Douglas-fir beetle, previously only available in multistep syntheses, [6] the R configuration could be assigned to the product 3 based on the reported optical rotation.The formation of 3 from 2 appears to be the first example of an enantioselective Rh-catalyzed 1,2-addition to an enone; thus, the reaction conditions were optimized. [7,8] On lowering the temperature to 0 8C or À20 8C the enantioselectivity was only slightly increased to 98 % ee, while the reaction was significantly retarded (Table 1, entries 1-3). Variation of the precatalyst led to similar results when starting from complexes with noncoordinating or bidentate counterions (Table 1, entries 4 and 5), yet significant improvements were achieved when using [{Rh(cod)OMe} 2 ], thus increasing the yield to 97 % with 99 % ee (entry 6). In a second set of experiments the catalyst loading was reduced, which still gave good results with 1 mol %, but almost no conversion with 0.1 mol % (Table 1, entries 7-9).Furthermore, the influence of the solvent was examined, revealing that THF is the best choice. With other ethers the yield decreased in the order 1,2-dimethoxyethane > dioxane > Et 2 O; hydrocarbons such as toluene proved unsuitable owing to significant background reactivity.[9] To gain insight into the sudden change of the reaction course, various monoand bidentate phosphine ligands were tested (PPh 3 , PnBu 3 , dppe, dppb, diop), [10] yet none of them led to the formation of the 1,4-adduct 1 or the 1,2-adduct 3 in more than 10 % yield. Furthermore, no conversion occurred in the presence of binap when omitting the Rh precatalyst, thus proving catalysis...