In the last decade, remarkable progress has been made toward the development of asymmetric reactions using organocatalysts under operationally simple and environmentally friendly reaction conditions.[1] Especially secondary amines derived from naturally available compounds worked as effective catalysts to promote asymmetric reactions of electrophiles with carbonyl compounds, such as aldol condensations and 1,4-conjugate additions, with high to excellent enantioselectivity.[2] In these reaction systems, enamines generated in situ from carbonyl compounds, such as aldehydes and ketones, and secondary amines worked as suitable carbon-centered nucleophiles. Nowadays, the methodology using organocatalysts realizes the diastereo-and enantioselective preparation of highly functionalized compounds such as (À)-Oseltamivir. [3,4] We have previously found that the ruthenium-catalyzed propargylic alkylation of propargylic alcohols with acetone as a carbon-centered nucleophile gives the corresponding products with a high enantioselectivity (up to 82 % ee). [5] Unfortunately, the use of an excess amount of simple ketones such as acetone was necessary to promote the propargylic alkylation. We have envisaged that the enamines generated in situ from aldehydes and secondary amines can be applied as carbon-centered nucleophiles for the asymmetric propargylic alkylation. As an extension of our study on enantioselective propargylic substitution reactions, [6] we have now found the ruthenium-catalyzed propargylic alkylation of propargylic alcohols with aldehydes in the presence of a catalytic amount of a secondary amine as an organocatalyst gives the corresponding products in high yields with an excellent enantioselectivity. In the present reaction system, both the transition-metal catalyst (ruthenium complex) and organocatalyst (secondary amine) activate the propargylic alcohol and aldehyde, respectively, thereby cooperatively promoting the enantioselective propargylic alkylation (Scheme 1). We believe that the method herein may provide a new type of dual catalytic reaction using both organocatalysts and transition-metal catalysts. [7,8] Preliminary results are described herein.Treatment of 1-phenyl-2-propyn-1-ol (1 a) with 3-phenylpropanal (2 a) in the presence of catalytic amounts of (S)-a,a,-bis[3,5-bis(trifluoromethyl)phenyl]-2-pyrrolidinemethanol trimethyl silyl ether (3 a), methanethiolate-bridged diruthenium complex [{Cp*RuCl(m 2 -SMe)} 2 ] (Cp* = h 5 -C 5 Me 5 ; 4 a), and NH 4 BF 4 in toluene at room temperature for 140 hours gave 2-benzyl-3-phenyl-4-pentynal (5 a) exclusively (Scheme 2). After the reduction of 5 a using NaBH 4 at 0 8C for one hour, 2-benzyl-3-phenyl-4-pentyn-1-ol (6 a) was isolated in 87 % yield as a mixture of two diastereoisomers (syn-6 a/anti-6 a = 2.2:1) with 94 % ee for syn-6 a and 88 % ee for anti-6 a. Only two equivalents of 2 a relative to 1 a were used as a carbon-centered nucleophile; this is in sharp contrast to the previous reaction system for propargylic alkylation, wherein a large amount (i.e.,...