Regioselective Aryne Annulations of <i>N</i>-Tosyl-2-enamides and <i>N</i>-<i>tert</i>-Butylsulfinyl-2-enamides for the Construction of Dihydroquinolin-4-one and Chroman-4-imine Units
Aimin Zhang, Suh Young Yu, Jihye Lee, Sehui Yang, Junseong Lee, Jimin Kim
IF 5
Organic Letters
A regioselective synthesis of the dihydroquinolin-4-one <b>4</b> is achieved from the aryne-mediated annulation of an <i>o</i>-(trimethylsilyl)aryl triflate <b>1</b> with <i>N</i>-tosyl-2-enamide <b>2</b> in the presence of TBAT in toluene, whereas the chroman-4-imine <b>5</b> is formed from the reaction of <b>1</b> with <i>N</i>-(<i>tert</i>-butylsulfinyl)-2-enamide <b>3</b> and TBAF in THF. Governing factors for regioselectivity have been accounted for as strong steric and electronic effects between <i>N</i>-toluenesulfonyl and <i>N</i>-<i>tert</i>-butylsulfinyl groups in <b>2</b> and <b>3</b>. The methods described herein are successful with various substrates <b>1</b> with <b>2</b> or <b>3</b> in high levels of regioselectivity, and diastereoselectivity for <b>5</b>.
Synthesis of (+)-Xylogiblactones B and C through a Kinetic Resolution of the Allenoate γ-Addition: Stereochemical Establishment
Aimin Zhang, Gyungah Pak, Suh Young Yu, Sehui Yang, Jimin Kim
IF 3.6
The Journal of Organic Chemistry
Concise syntheses of naturally occurring γ-butenolides (+)-xylogiblactones B and C have been achieved for the first time starting from commercial methyl crotonate in 5-8 steps. The synthetic course involves allenoate γ-addition to racemic aldehydes through a kinetic resolution to establish the required stereochemical framework as center and axial chirality and subsequent oxacyclization via gold catalysis to complete the (+)-xylogiblactone skeleton. Both key transformations proceed in a regio- and stereospecific manner. This outcome relies on finding an efficient synthetic method for racemic aldehydes as precursors for the kinetic resolution. Completion of the synthesis provides stereochemical clarification for (+)-xylogiblactones B and C.
Cyclocarbonylation of Allenyl Glyoxylate Strategy to Build the Tricyclic Core of Cyclocalopin A
Weonju Yu, Jieun Song, Suh Young Yu, Jimin Kim
IF 5
Organic Letters
An approach for the construction of the tricyclic framework of naturally occurring cyclocalopin A is described. The establishment of the crucial intermediate α-methylene bis-γ,δ-lactone involves a [2 + 2 + 1]-cyclocarbonylation of newly introduced allenyl glyoxylate via direct methods using Mo(CO)<sub>6</sub> or sequential reaction pathways. The sequential reaction route involved a stannylative cyclization by Pd(0) catalyst, bromination of an vinyl stannane moiety, and final cyclocarbonylation by palladium catalysis to provide the bis-γ,δ-lactone. The feasibility of forming the spiro-system by an <i>exo</i>-selective [4 + 2]-cycloaddition was accomplished.
Synthesis of (+)-Hypoxylactone through Allenoate γ-Addition: Revision of Stereochemistry
Gyungah Pak, Euijin Park, Saehansaem Park, Jimin Kim
IF 3.6
The Journal of Organic Chemistry
A synthesis of (+)-hypoxylactone has been accomplished in four steps starting from the allenoate γ-addition of <i>threo</i>-3-chloro-2-silyoxybutanals, leading to the revision of stereochemistry. The key was the discovery of control elements required to matching/mismatching cases in the allenoate γ-addition to provide the desired adducts as a single isomer. The utility of the γ-adduct was demonstrated with the Au(I)-catalyzed cyclization to afford (+)-xylogiblactone A. Use of Ag<sub>2</sub>O was the key to epoxidation for preventing epimerization of the γ-lactone ring.
Kinetic Resolution of Racemic Aldehydes through Asymmetric Allenoate γ-Addition: Synthesis of (+)-Xylogiblactone A
Saehansaem Park, Gyungah Pak, Changhwa Oh, Jieun Lee, Jimin Kim, Chan‐Mo Yu
IF 5
Organic Letters
A synthesis of (+)-xylogiblactone A has been achieved from <i>t</i>-butyl 2-methylbuta-2,3-dienoate in a linear three-step sequence. The key elements of the synthesis include a kinetic resolution of racemic 2-silyoxyaldehyde through the allenoate γ-addition to yield the γ-adduct as a single isomer and the subsequent gold catalysis to form the butenolide core. For a general method, the kinetic resolution of several racemic 2-silyloxyaldehydes is also performed to provide products in high levels of stereoselectivity with unusual <i>anti</i>-Felkin-Anh addition fashion.
Kinetic resolution of dihydroquinolines via Ru( <scp>II</scp> )‐ <scp>TsDPEN</scp> ‐catalyzed asymmetric transfer hydrogenation
Suh Young Yu, Jihye Lee, Aimin Zhang, Jimin Kim
IF 2.2
Bulletin of the Korean Chemical Society
Abstract The kinetic resolution of 2‐substituted tetrahydro‐4‐quinolone derivatives ( N ‐tosyl azaflavones) has been accomplished by Ru(II)‐TsDPEN‐catalyzed asymmetric transfer hydrogenation (ATH). Employing HCO 2 Na in the presence of a phase transfer catalyst as the hydrogen source, this methodology proceeds under mild and operationally convenient conditions. The process provides access to enantiomerically enriched 2‐substituted‐ N ‐tosyl‐2,3‐dihydroquinolin‐4(1H)‐ones with excellent levels of enantioselectivity, frequently exceeding 99% ee. In parallel, the corresponding 2‐substituted‐1‐tosyl‐1,2,3,4‐tetrahydroquinolin‐4‐ols are obtained in high conversion, also with superior enantioselectivity up to >99% ee. Both product classes are of considerable synthetic utility, and the high selectivity factors observed underscore the efficiency of this ATH approach. Overall, these results demonstrate the value of Ru(II)‐TsDPEN catalysis combined with HCO 2 Na/PTC as a practical strategy for the enantioselective synthesis of structurally diverse azaflavone derivatives.
Regioselective Aryne Annulations of <i>N</i>-Tosyl-2-enamides and <i>N</i>-<i>tert</i>-Butylsulfinyl-2-enamides for the Construction of Dihydroquinolin-4-one and Chroman-4-imine Units
Aimin Zhang, Suh Young Yu, Jihye Lee, Sehui Yang, Junseong Lee, Jimin Kim
IF 5
Organic Letters
A regioselective synthesis of the dihydroquinolin-4-one <b>4</b> is achieved from the aryne-mediated annulation of an <i>o</i>-(trimethylsilyl)aryl triflate <b>1</b> with <i>N</i>-tosyl-2-enamide <b>2</b> in the presence of TBAT in toluene, whereas the chroman-4-imine <b>5</b> is formed from the reaction of <b>1</b> with <i>N</i>-(<i>tert</i>-butylsulfinyl)-2-enamide <b>3</b> and TBAF in THF. Governing factors for regioselectivity have been accounted for as strong steric and electronic effects between <i>N</i>-toluenesulfonyl and <i>N</i>-<i>tert</i>-butylsulfinyl groups in <b>2</b> and <b>3</b>. The methods described herein are successful with various substrates <b>1</b> with <b>2</b> or <b>3</b> in high levels of regioselectivity, and diastereoselectivity for <b>5</b>.
Synthesis of (+)-Xylogiblactones B and C through a Kinetic Resolution of the Allenoate γ-Addition: Stereochemical Establishment
Aimin Zhang, Gyungah Pak, Suh Young Yu, Sehui Yang, Jimin Kim
IF 3.6
The Journal of Organic Chemistry
Concise syntheses of naturally occurring γ-butenolides (+)-xylogiblactones B and C have been achieved for the first time starting from commercial methyl crotonate in 5-8 steps. The synthetic course involves allenoate γ-addition to racemic aldehydes through a kinetic resolution to establish the required stereochemical framework as center and axial chirality and subsequent oxacyclization via gold catalysis to complete the (+)-xylogiblactone skeleton. Both key transformations proceed in a regio- and stereospecific manner. This outcome relies on finding an efficient synthetic method for racemic aldehydes as precursors for the kinetic resolution. Completion of the synthesis provides stereochemical clarification for (+)-xylogiblactones B and C.
Cyclocarbonylation of Allenyl Glyoxylate Strategy to Build the Tricyclic Core of Cyclocalopin A
Weonju Yu, Jieun Song, Suh Young Yu, Jimin Kim
IF 5
Organic Letters
An approach for the construction of the tricyclic framework of naturally occurring cyclocalopin A is described. The establishment of the crucial intermediate α-methylene bis-γ,δ-lactone involves a [2 + 2 + 1]-cyclocarbonylation of newly introduced allenyl glyoxylate via direct methods using Mo(CO)<sub>6</sub> or sequential reaction pathways. The sequential reaction route involved a stannylative cyclization by Pd(0) catalyst, bromination of an vinyl stannane moiety, and final cyclocarbonylation by palladium catalysis to provide the bis-γ,δ-lactone. The feasibility of forming the spiro-system by an <i>exo</i>-selective [4 + 2]-cycloaddition was accomplished.
Synthesis of (+)-Hypoxylactone through Allenoate γ-Addition: Revision of Stereochemistry
Gyungah Pak, Euijin Park, Saehansaem Park, Jimin Kim
IF 3.6
The Journal of Organic Chemistry
A synthesis of (+)-hypoxylactone has been accomplished in four steps starting from the allenoate γ-addition of <i>threo</i>-3-chloro-2-silyoxybutanals, leading to the revision of stereochemistry. The key was the discovery of control elements required to matching/mismatching cases in the allenoate γ-addition to provide the desired adducts as a single isomer. The utility of the γ-adduct was demonstrated with the Au(I)-catalyzed cyclization to afford (+)-xylogiblactone A. Use of Ag<sub>2</sub>O was the key to epoxidation for preventing epimerization of the γ-lactone ring.
Kinetic Resolution of Racemic Aldehydes through Asymmetric Allenoate γ-Addition: Synthesis of (+)-Xylogiblactone A
Saehansaem Park, Gyungah Pak, Changhwa Oh, Jieun Lee, Jimin Kim, Chan‐Mo Yu
IF 5
Organic Letters
A synthesis of (+)-xylogiblactone A has been achieved from <i>t</i>-butyl 2-methylbuta-2,3-dienoate in a linear three-step sequence. The key elements of the synthesis include a kinetic resolution of racemic 2-silyoxyaldehyde through the allenoate γ-addition to yield the γ-adduct as a single isomer and the subsequent gold catalysis to form the butenolide core. For a general method, the kinetic resolution of several racemic 2-silyloxyaldehydes is also performed to provide products in high levels of stereoselectivity with unusual <i>anti</i>-Felkin-Anh addition fashion.
