Masahiro Anada

Dirhodium(II) tetrakis[N-tetrachlorophthaloyl-(S)-tert-leucinate]: a new chiral Rh(II) catalyst for enantioselective amidation of CH bonds

Abstract Dirhodium(II) tetrakis[N-tetrachlorophthaloyl-(S)-tert-leucinate], characterized by substitution of chlorine atoms for four hydrogen atoms on the phthalimido group in the parent dirhodium(II) complex has been found to be well suited for enantioselective amidation of benzylic CH bonds with [(4-nitrophenyl)sulfonylimino]phenyliodinane. The observed enantioselectivity of up to 84% ee is the highest reported to date for dirhodium(II) complex-catalyzed CH amidations.

Catalytic Enantioselective Intermolecular Cycloaddition of 2-Diazo-3,6-diketoester-Derived Carbonyl Ylides with Alkynes and Styrenes Using Chiral Dirhodium(II) Carboxylates

Dirhodium(II) tetrakis[ N-tetrachlorophthaloyl-( S)- tert-leucinate], Rh 2( S-TCPTTL) 4, is an exceptionally effective catalyst for enantioselective tandem carbonyl ylide formation-cycloaddition reactions of 2-diazo-3,6-diketoesters with arylacetylene, alkoxyacetylene, and styrene dipolarophiles, providing cycloadducts in good to high yields and with enantioselectivities of up to 99% ee as well as with perfect exo diastereoselectivity for styrenes.

Enantioselective Synthesis of 4-Substituted 2-Pyrrolidinones by Site-selective C-H Insertion of α-Methoxycarbonyl-α-diazoacetanilides Catalyzed by Dirhodium(II) Tetrakis[N-phthaloyl-(S)-tert-leucinate]

Abstract Site- and enantioselective intramolecular CH insertion of α-methoxycarbonyl-α-diazoacetamides has been achieved by exploiting a p-nitrophenyl group as the N-substituent and dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate] as catalyst, leading to the formation of 4-substituted 2-pyrrolidinone derivatives of up to 82% ee. The efficiency of the present protocol has been verified well by a short-step synthesis of (R)-(−)-baclofen .

Dirhodium(II) tetrakis[N-tetrafluorophthaloyl-(S)-tert-leucinate]: an exceptionally effective Rh(II) catalyst for enantiotopically selective aromatic C–H insertions of diazo ketoesters

Abstract Dirhodium(II) tetrakis[ N -tetrafluorophthaloyl-( S )- tert -leucinate], Rh 2 [( S )-TFPTTL] 4 , in which the phthalimido hydrogen atoms of the parent dirhodium(II) complex are substituted by fluorine atoms, dramatically enhances the reactivity and enantioselectivity (up to 97% ee) in intramolecular aromatic C–H insertion reactions of methyl 4-alkyl-2-diazo-4,4-diphenyl-3-oxopropionates. Catalysis with the use of 0.001 mol% of Rh 2 [( S )-TFPTTL] 4 has achieved the highest turnover number (up to 98,000 with the methyl substituent) ever recorded for chiral dirhodium(II) complex-catalyzed carbene transformations, without compromising the yield or enantioselectivity of the process.

Enantioselective intermolecular 1,3-dipolar cycloaddition via ester- derived carbonyl ylide formation catalyzed by chiral dirhodium(II) carboxylates

Enantioselective 1,3-dipolar cycloaddition of the ester-carbonyl ylides derived from methyl 2-(diazoacetyl)benzoate and 3-(diazoacetyl)-2-naphthoate with dipolarophiles has been effected with the aid of dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate], affording cycloadducts in up to 93% ee.

Enantioselective [2,3]-sigmatropic and [1,2]-Stevens rearrangements via intramolecular formation of allylic oxonium ylides catalyzed by chiral dirhodium(II) carboxylates

Abstract Tandem intramolecular generation and rearrangement of allylic oxonium ylides from α-diazo β-keto esters has been effected with the aid of dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate] in toluene, providing benzofuran-3-ones via [2,3]-sigmatropic rearrangement in up to 76% ee. In systems with crotyl and prenyl substituents, products arising from the less common [1,2]-Stevens rearrangement as a side reaction have also been obtained in up to 66% ee. It is suggested that competitive [2,3]- and [1,2]-rearrangements proceed through a common, chiral rhodium(II)-bound oxonium ylide intermediate.

Catalytic Asymmetric Synthesis of the endo-6-Aryl-8-oxabicyclo[3.2.1]oct-3-en-2-one Natural Product from Ligusticum chuanxing via 1,3-Dipolar Cycloaddition of a Formyl-Derived Carbonyl Ylide Using Rh2(S-TCPTTL)4

The reaction of a six-membered cyclic formyl-carbonyl ylide derived from alpha-diazo-beta-ketoester with phenylacetylene derivatives under the catalysis of dirhodium(II) tetrakis[N-tetrachlorophthaloyl-(S)-tert-leucinate], Rh(2)(S-TCPTTL)(4), provides cycloadducts containing an 8-oxabicyclo[3.2.1]octane ring system in up to 97% ee. This represents the first example of an enantioselective 1,3-dipolar cycloaddition of a cyclic formyl-carbonyl ylide. Using this catalytic process, an asymmetric synthesis of endo-6-aryl-8-oxabicyclo[3.2.1]oct-3-en-2-one natural product 1 from Ligusticum chuanxing Hort. has been achieved.

Enantioselective intramolecular CH insertion route to a key intermediate for the synthesis of trinem antibiotics

A new route to the enantiomerically pure azetidin-2-one 3, a key intermediate for the synthesis of trinems, has been developed, incorporating enantioselective intramolecular CH insertion of α-methoxycarbonyl-α-diazoacetamide catalyzed by chiral Rh(II) complexes and diastereoselective arene hydrogenation as the key steps. The use of dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate] as a catalyst produced the desired azetidinone in 84% ee, whereas catalysis with dirhodium(II) tetrakis[N-phthaloyl-(S)-alaninate] afforded its enantiomer in 84% ee.

Enantioselective SiH insertion of methyl phenyldiazoacetate catalyzed by dirhodium(II) carboxylates incorporating N-phthaloyl-(S)-amino acids as chiral bridging ligands

Abstract Enantioselective insertion reactions of methyl phenyldiazoacetate into the SiH bond of silanes were effected by employing dirhodium(II) carboxylates incorporating N -phthaloyl-( S )-amino acids as chiral bridging ligands. The use of dirhodium(II) tetrakis[ N -phthaloyl-( S )-phenylalaninate] as a catalyst produced methyl (2 S )-(dimethylphenylsilyl)phenylacetate in 74% ee, whereas catalysis with dirhodium(II) tetrakis[ N -phthaloyl-( S )-phenylglycinate] afforded its enantiomer in 72% ee.

Asymmetric Total Synthesis of (−)‐Englerin A through Catalytic Diastereo‐ and Enantioselective Carbonyl Ylide Cycloaddition

An asymmetric total synthesis of the guaiane sesquiterpene (-)-englerin A, a potent and selective inhibitor of the growth of renal cancer cell lines, was accomplished. The basis of the approach is a highly diastereo- and enantioselective carbonyl ylide cycloaddition with an ethyl vinyl ether dipolarophile under catalysis by dirhodium(II) tetrakis[N-tetrachlorophthaloyl-(S)-tert-leucinate], [Rh2 (S-TCPTTL)4 ], to construct the oxabicyclo[3.2.1]octane framework with concomitant introduction of the oxygen substituent at C9 on the exo-face. Another notable feature of the synthesis is ruthenium tetraoxide-catalyzed chemoselective oxidative conversion of C9 ethyl ether to C9 acetate.