Synthesis of 1,2-Diamino Acid Derivatives Utilizing Diastereoselective Tandem N-Alkylation/Homo- and Cross-Addition Reaction of $$\alpha $$ α -Aldimino Thioesters

Umpolung Chemo- and Regioselective Cascade Addition of Diethylzinc to α-Diketones Followed by Intramolecular Michael Reaction: Stereoselective Synthesis of Highly Substituted 1- Indanones

Herein we report an efficient stereoselective umpolung 1,2-addition of Et₂Zn onto α-diketones followed by intramolecular cascade Michael cyclization. This strategy effectively delivers a broad range of substituted 1-indanones in excellent yields in a chemo- and regioselective fashion. Additionally, we performed a variety of synthetic transformations on the 1-indanone products. Furthermore, a hitherto-unexplored asymmetric variant of this methodology that provides up to 94:6 er using an easily accessible cinchona alkaloid ligand has been addressed.

N-Alkylation/aldol reaction of α-aldimino thioesters: a facile three-component coupling reaction

Theoretical calculation of the reactivity of α-imino thioesters indicates that they are very reactive substrates for Umpolung N-alkylation. In fact, treatment of α-aldimino thioesters with dialkylzinc reagents in the presence of aldehydes or imines gives three-component coupling products in good yields.

Synthesis of Tetramic Acid Derivatives via a Tandem Umpolung Alkylation/Reduction/Cyclization Reaction of γ-Hydrazono β-Ketoester

An efficient method for the one-pot synthesis of tetramic acid derivatives was developed utilizing tandem umpolung N-alkylation/reduction/cyclization of γ-hydrazono β-ketoester. By using this reaction as a key step, the total synthesis of the 3-spiro 7-hydroxamic acid tetralin which possesses an HDAC inhibitory activity was also achieved.

An umpolung reaction of α-iminothioesters possessing a cyclopropyl group

An umpolung N-alkylation reaction of α-cyclopropyl α-iminothioesters with diethylaluminum chloride or ethylmagnesium bromide affords the corresponding N-ethylated α-aminothioesters in good yields. Subsequent oxidation and reaction of the N-ethylated product with a thiolate or a chloride anion proceed effectively to give the ring-opened products in good yields. In contrast, relatively “hard” nucleophiles did not give the ring-opened products but gave the addition products to the iminium carbon.

Tandem N-alkylation/oxidation/second addition reaction to α-cyclopropyl α-imino(thio)esters gave N-alkylated ring-opened products in good yields.

Tandem N, N-Dialkylation Reaction of N-Trimethylsilyl α-Iminoesters Utilizing an Umpolung Reaction and Characteristics of the Silyl Substituent: Synthesis of Pyrrolidine, Piperidine, and Iminodiacetate

Umpolung reactions of N-trimethylsilyl α-iminoester with organometallics gave directly N-alkylaminoesters in high yields without the need for removing a protecting group at the nitrogen atom. Efficient syntheses of pyrrolidines, piperidines, and iminodiacetate derivatives were also developed via tandem N,N- or N, C-dialkylation reactions utilizing characteristics of the silyl substituent. Furthermore, under the influence of silica gel, the addition of an enolate to the imino nitrogen proceeded to give an iminodiacetate derivative.

A facile approach to 2-alkoxyindolin-3-one and its application to the synthesis of N-benzyl matemone

2-Alkoxycarbonylindolin-3-one is synthesized from a methoxyglycine derivative via a 1,2-aza-Brook rearrangement followed by cyclization with bis(trimethylsilyl)aluminum chloride. A short-step synthesis of N-benzyl matemone is successfully carried out using the present indolin-3-one synthesis.

A short-step synthesis of N-benzyl matemone has been successfully carried out using a newly discovered 2-ethoxycarbonylindolin-3-one synthesis.

Umpolung Reaction of α-Imino Thioesters and the Subsequent C-C Bond Formation with the Unexpected Alkylthio Rearrangement

An umpolung reaction of the α-imino thioester was examined, and we found that α-imino thioesters were more effective substrates for the umpolung N-alkylation than conventional α-imino esters and they gave N-alkylated amino thioesters in high yields under mild reaction conditions in a short time. A new type of C-C bond formation followed by an unexpected rearrangement of the alkylthio group took place with the unsaturated ketones to afford the β-alkylthio-α-amino thioesters in high yields with good diastereoselectivity.