Kazuhisa Funakoshi

Asymmetric cyclization reactions. Cyclization of substituted 4-pentenals into cyclopentanone derivatives by rhodium(I) with chiral ligands

Abstract Asymmetric cyclization of substituted 4-pentenals ( Ia,b,c; IIa,b,c,d ) by Rh(I) with chiral ligands was tested, and substrate ( IId ) with a bulkier substituent at C 4 underwent more stereoselective cyclization by Rh(I)-((+)-DIPMC) to yield substituted cyclepentanone ( IIID ). The Rh(I) with (+)-DIPMC was found to proceed in a different manner from the Wilkinson-catalyzed cyclization.

Asymmetric cyclization reactions by Rh(I) with chiral ligands

Abstract Cyclization of prochiral 4-butyl-4-penten-1-al by Rh(I)-complex with chiral phosphine ligand afforded 4-butylcyclopentanone with 73% ee. 3(S),4-Disubstituted 4-penten-1-al and 3(R)-isomer were preferentially cyclized to cis-cyclopentanone and trans-cyclopentanone, respectively.

A novel synthesis of cis-3,4-disubstituted cyclopentanones

Abstract A new method for the stereospecific synthesis of cis-3,4-disubstituted cyclopentanones is described.

Highly enantioselective cyclization using cationic Rh(I) with chiral ligand

Abstract Highly diastereoselective cyclization (>99% de) of 3R (or S) 3,4-disubstituted 4-pentenals into the corresponding 3,4-cis(or trans)-disubstituted cyclopentanone and highly enantioselective cyclization (>99% ee) of 4-substituted 4-pentenals into 3-substituted cyclopentanone were achieved by using cationic Rh + (BINAP)ClO 4 − .

Highly diastereoselective, enantioselective cyclization of symmetrical 3,4-disubstituted 4-pentenal using chiral rhodium(I)-complex

Abstract Concurrent introduction of two chiral centers at 3,4-positions of cyclopentanone from symmetrical 1 was achieved in diastereoselective and enantioselective fashion by combination of BINAP and cationic Rh(I)(or neutral).

Enantio- and diastereoselective construction of 4,9-dimethylspiro[4.4]nonane-2,7-dione using Rh-catalyzed asymmetric cyclization

Abstract Asymmetric cyclization using Rh-complexes was applied to the synthesis of 4,9-dimethylspiro[4.4]nonane-2,7-diones. The spiro[4.4]nonane skeleton bearing a chiral quaternary carbon could be stepwisely constructed by using Rh-catalyzed cyclization twice. All diastereomers of the spirodiketone could be stereoselectively prepared from the identical starting material by the combination of a neutral Rh(PPh3)3Cl and a cationic Rh[BINAP]ClO4. The cyclization by the neutral Rh(PPh3)3Cl proceeded to give cis-3,4-disubstituted cyclopentanones, while that by the cationic Rh[BINAP]ClO4 proceeded to afford trans-3,4-disubstituted cyclopentanones. Four spirodiketones of six stereoisomers could be prepared in optically active form, and the relationship between the stereochemistry of the spirodiketones and the Rh-complex was discussed based on the plausible acyl-hydride Rh-complexes.

Diastereoselective cyclization of 6-octen-1-als with rhodium(I)-complex

Abstract Rhodium(I)-catalyzed cyclization of 6-octen-1-al with chiral protecting group ((4R,6R)-dimethyl-1,3-dioxane) at the C 3 afforded diastereoselectively the trans-cyclohexanol.

Application of Rh-catalyzed cyclization for the construction of three consecutive chiral carbons in 4,9-dimethylspiro[4.4]nonane-2,7-dione

Asymmetric cyclization using Rh-complexes has been applied to the synthesis of 4,9-dimethylspiro[4.4]nonane-2,7-diones. The spiro[4.4]nonane skeleton bearing three consecutive chiral carbons could be stepwisely constructed from an identical starting material by the combination of a cationic Rh[(S)-BINAP]ClO4 and a neutral RhCl(PPh3)3. The relationship between the stereochemistry of the spirodiketones and the Rh-complex was also discussed.

Insight into Rh(I)-catalyzed cyclization of 6-octen-1-als with a chiral protecting group

Abstract Rh(I)(Wilkinson)[ClRh(PPh3)3]-catalyzed cyclization of 6-octen-1-als with a chiral protecting group at the C2-position afforded only cis-cyclohexanol derivatives, and in the case of C4-position yielded a mixture of cis and trans cyclohexanol. These findings were remarkably different from the case of the C3-position, in which the trans cyclohexanol derivative was obtained. Wilkinsons complex acts as [ClRh(PPh3)3] a Lewis acid, and this bulkier Lewis acid affords higher diastereoselectivity. Rh(I)-catalyzed cyclization of 6-octen-1-at derivatives is not affected by chiral ligands.

Rh(I)-catalyzed formation of two conformers due to cis-1,2-cyclohexanediol

Abstract Two 6-octen-1-als (I and II) with cis-1,2-cyclohexanedioxy function at the C 3 -position are cyclized by Rh(I)-complex(Wilkinson-complex) to afford two conformers due to cis-cyclohexanediol, respectively.