Search

The CuBr2-catalyzed enantioselective allenylation of terminal alkynols with carbon chains of different lengths has been developed. Compared with (S)-α,α-diphenylprolinol, the reaction using (S)-α,α-dimethylprolinol as the chiral amine afforded optically active 1,3-disubstuted allenols with higher ee-values. Both aliphatic and aromatic aldehydes could be applied. The naturally occurring phlomic acid was synthesized in four steps from commercially available hex-5-yn-1-ol. [ABSTRACT FROM AUTHOR]

A comprehensive study on aerobic oxidation of benzylic alcohols to carboxylic acids with a catalytic amount each of Fe(NO3)3·9H3O, TEMPO, and KCl is conducted. Various synthetically useful functional groups are well tolerated in the reaction. Distinct electronic and steric effects are observed in the reaction: electron-withdrawing groups accelerate the reaction while electron-donating groups make the reaction slower, and ortho-substituted substrates react slower than meta-substituted substrates. Several large-scale reactions (100 mmol) are conducted using a slow air flow of 30 mL/min to demonstrate the practicality of this method in an academic laboratory. [ABSTRACT FROM AUTHOR]

A first practical Ni(0)-catalyzed highly stereoselective methyl-carboxylation of homopropargylic alcohols with ZnMe2and CO2for the efficient synthesis of α-alkylidene-γ-butyrolactones is described. The reaction may be applied to other alkynols. [ABSTRACT FROM AUTHOR]

A highly regioselective Cu(I)-catalyzed anti-carbometallation of secondary terminal propargylic alcohols with 1° alkyl or aryl Grignard reagents affording 2-substituted allylic alcohols was developed. By using this method, optically active allylic alcohols can be prepared from the optically active propargylic alcohols without obvious loss of the enantiopurity. The cyclic organometallic intermediate formed may undergo an iodination or a Pd(0)-catalyzed coupling reaction to afford stereo-defined allylic alcohols. [ABSTRACT FROM AUTHOR]

Studies the mechanism of anti-carbometalation of homopropargyl alcohols and their higher homologues. Differences in the ease and scope between stereoisomerization of the omega-alkynols and its derivative; Preferential formation of an eight membered aluminacycle.

Recently, we have developed highly regio- and stereoselective carbometalation of 2-alkynols and 2,3-allenols. The organometallacyclic intermediates may be trapped with I2 to afford 3-iodoalk-2-en-l-ols. These 3-iodoalk-2-en-l-ols may readily undergo the Sonogashira coupling with terminal propargyl alcohols to form 4-alkyn-2-ene-1,6-diols. Subsequent cycloisomerization in DMA or CH2CI2 with Au(PPh3)Cl and AgOTf as the catalyst would afford polysubstituted 2-( 1-alkenyl)furans; with PdCl2 as the catalyst and the reaction in DMA in the presence of allylic bromides, the same substrates afforded polysubstituted 2-( 1,4- alkadienyl)furans. In both types of catalyzed cyclization reactions, the elimination of H2O promoted the aromatization to form the furan ring. Different alkyl or aryl groups could be introduced into different positions of furans due to the substituent-loading capability of 3-iodoalkenols and diversity of the terminal propargyl alcohols and allylic bromides. [ABSTRACT FROM AUTHOR]

The sequential treatment of optically active terminal propargylic alcohols with n-BuLi/(HCHO). and regioselective chlorination afforded the corresponding optically active 4-chloro-2-butyn-1-ols. With R¹ being a methyl or an ethyl group, an alternative for the synthesis of the corresponding optically active propargylic alcohols is the Novozym 435- catalyzed kinetic resolution of these racemic 4-chloro-2- butyn-1-ols. The subsequent reaction of these optically active 4-chloro-2-butyn-1-ols with the corresponding Grignard reagents under the catalysis of 5 mol % of CuCN afforded the optically active secondary 2,3-allenols in good yields with up to >99% ee. [ABSTRACT FROM AUTHOR]