Shinji Kitagaki

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 Cue5f8H 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 Cue5f8H amidations.

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.

Toward the second-generation synthesis of zaragozic acids: Construction of the 2,8-dioxabicyclo[3.2.1]octane core system via tandem carbonyl ylide Formation and 1,3-dipolar cycloaddition sequence

Abstract A highly efficient construction of the 2,8-dioxabicyclo[3.2.1]octane core structure of zaragozic acids, inhibitors of the enzyme squalene synthase, has been achieved by exploiting the sequence of rhodium(II)-mediated intramolecular carbonyl ylide formation from an α-diazo ester and stereocontrolled 1,3-dipolar cycloaddition with (E)-3-hexene-2,5-dione.

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 Siue5f8H 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.

Enantioselective tandem formation and [2,3]-sigmatropic rearrangement of cyclic propargylic oxonium ylides catalyzed by dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate]

This paper describes the first examples of catalyst-dependent asymmetric induction in the periselective [2,3]-sigmatropic rearrangement of propargylic oxonium ylides generated by catalytic diazo decomposition. Catalysis of α-diazo-s-keto esters 4a—g using dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate] in toluene has led to the virtually exclusive formation of benzofuran-3-ones bearing an allenic group with up to 79% ee.

Enantioselective Intramolecular C-H Amidation of Sulfamate Esters Catalyzed by Chiral Dirhodium(II) Carboxylates

The chiral dirhodium(II) carboxylate-catalyzed enantioselective intramolecular C-H amidation reaction of sulfamate esters via in situ generated iminoiodinanes is described. The use of dirhodium(II) tetrakis[N-tetrafluorophthaloyl-(S)-tert-leucinate], Rh 2 (S-TFPTTL) 4 , as a catalyst and PhI(OAc) 2 as an oxidant provides cyclic sulfamidates in up to 48% ee.

Catalytic asymmetric synthesis of 1,1′-spirobi[indan-3,3′-dione] via a double intramolecular C–H insertion process

A highly efficient one-pot construction of optically active 1,1-spirobi[indan-3,3-dione] derivative (up to 80% ee) has been achieved by exploiting the double intramolecular C-H insertion reaction of dimethyl 2,2-methylenebis(alpha-diazo-beta-oxobenzenepropanoate) under the influence of dirhodium(II) tetrakis[N-phthaloyl-(R or S)-tert-leucinate] as a catalyst.