Unexpected Facile Sequential Halolactamization−Hydroxylation of 2,3-Allenamides with CuX₂ for the Efficient Synthesis of 4-Halo-5-hydroxypyrrol-2(5<i>H</i>)-ones^†

4-Halo-5-hydroxypyrrol-2(5H)-ones were synthesized from the efficient sequential halolactamization−hydroxylation reaction of 4-monosubstituted 2,3-allenamides with CuX2 (X = Br, Cl) in high yields. Halolactamization of fully substituted 2,3-dienamide (1f) afforded 4-halo-pyrrol-2(5H)-ones

Steric Hindrance-Controlled Pd(0)-Catalyzed Coupling−Cyclization of 2,3-Allenamides and Organic Iodides. An Efficient Synthesis of Iminolactones and γ-Hydroxy-γ-lactams

Under the catalysis of 1 mol % Pd(PPh3)4, the reaction of 4,4-disubstituted 2,3-allenamides and organic iodides in toluene afforded iminolactones stereospecifically in >90% yields using K2CO3 (2 equiv)−5 mol % TBAB as the base. A similar reaction with 4-monosubstituted 2,3-allenamides afforded γ-hydroxy-γ-lactams in relatively lower yields. The N/O-attack selectivity may be determined by the steric effect at the 4-position of 2,3-allenamides

Hydrohalogenation Reaction of 1,2-Allenyl Ketones Revisited. Efficient and Highly Stereoselective Synthesis of β,γ-Unsaturated β-Haloketones

Hydrohalogenation Reaction of 1,2-Allenyl Ketones Revisited. Efficient and Highly Stereoselective Synthesis of β,γ-Unsaturated β-Haloketone

Catalytic Asymmetric oxa-Michael−Michael Cascade for Facile Construction of Chiral Chromans via an Aminal Intermediate

An unprecedented highly enantioselective cascade oxa-Michael−Michael reaction has been developed. The simple and practical process, efficiently catalyzed by chiral diphenylprolinol TMS ether, affords a powerful access to highly functionalized synthetically useful chiral chromans. Moreover, notably a new activation mode involving an aminal is disclosed for the first time

Catalytic Asymmetric oxa-Michael−Michael Cascade for Facile Construction of Chiral Chromans via an Aminal Intermediate

An unprecedented highly enantioselective cascade oxa-Michael−Michael reaction has been developed. The simple and practical process, efficiently catalyzed by chiral diphenylprolinol TMS ether, affords a powerful access to highly functionalized synthetically useful chiral chromans. Moreover, notably a new activation mode involving an aminal is disclosed for the first time

Highly Enantioselective Aldol Reactions Catalyzed by a Recyclable Fluorous (<i>S</i>) Pyrrolidine Sulfonamide on Water

Fluorous (S) pyrrolidine sulfonamide serves as an efficient promoter for highly enantioselective aldol reactions of ketones and aldehydes with aromatic aldehydes on water. A notable feature of the organocatalyst is that it can be recovered from the reaction mixtures by simple fluorous solid-phase extraction and subsequently reused (up to seven cycles) without a significant loss of catalytic activity and stereoselectivity

Organocatalytic Enantioselective Cascade Michael-Alkylation Reactions: Synthesis of Chiral Cyclopropanes and Investigation of Unexpected Organocatalyzed Stereoselective Ring Opening of Cyclopropanes

The development of efficient methods for the facile construction of important molecular architectures is a central goal in organic synthesis. An unprecedented organocatalytic asymmetric cascade Michael-alkylation reaction of α,β-unsaturated aldehydes with bromomalonates has been developed. The process, efficiently catalyzed by chiral diphenylprolinol TMS ether in the presence of base 2,6-lutidine, serves as a powerful approach to the preparation of synthetically and biologically important cyclopropanes in high levels of enantio- and diastereoselectivities. Remarkably, the power of the cascade process is fueled by its high efficiency of the production of two new C−C bonds, two new stereogenic centers, and one quaternary carbon center in one single operation, which otherwise is difficult to achieve by traditional strategies. Moreover, the beauty of the cascade process is further underscored by the nature of the product formation depending on the reaction conditions. With the alternation of base from 2,6-lutidine (1.1 equiv), which is effective for the cyclopropanations, to NaOAc (4.0 equiv), the spontaneous ring-opening of cyclopropanes takes place to lead to stereoselective (E) α-substituted malonate α,β-unsaturated aldehydes. A possible reaction mechanism, which involves a Michael-alkylation−retro-Michael pathway, is proposed and verified by experimental studies. This investigation represents the first example of an organocatalyst-promoted ring opening of the cyclopropanes, whereas such reactions have been intensively explored by Lewis acid-based catalysis

Organocatalytic Enantioselective Cascade Michael-Alkylation Reactions: Synthesis of Chiral Cyclopropanes and Investigation of Unexpected Organocatalyzed Stereoselective Ring Opening of Cyclopropanes

The development of efficient methods for the facile construction of important molecular architectures is a central goal in organic synthesis. An unprecedented organocatalytic asymmetric cascade Michael-alkylation reaction of α,β-unsaturated aldehydes with bromomalonates has been developed. The process, efficiently catalyzed by chiral diphenylprolinol TMS ether in the presence of base 2,6-lutidine, serves as a powerful approach to the preparation of synthetically and biologically important cyclopropanes in high levels of enantio- and diastereoselectivities. Remarkably, the power of the cascade process is fueled by its high efficiency of the production of two new C−C bonds, two new stereogenic centers, and one quaternary carbon center in one single operation, which otherwise is difficult to achieve by traditional strategies. Moreover, the beauty of the cascade process is further underscored by the nature of the product formation depending on the reaction conditions. With the alternation of base from 2,6-lutidine (1.1 equiv), which is effective for the cyclopropanations, to NaOAc (4.0 equiv), the spontaneous ring-opening of cyclopropanes takes place to lead to stereoselective (E) α-substituted malonate α,β-unsaturated aldehydes. A possible reaction mechanism, which involves a Michael-alkylation−retro-Michael pathway, is proposed and verified by experimental studies. This investigation represents the first example of an organocatalyst-promoted ring opening of the cyclopropanes, whereas such reactions have been intensively explored by Lewis acid-based catalysis

Organocatalytic Enantioselective Cascade Michael-Alkylation Reactions: Synthesis of Chiral Cyclopropanes and Investigation of Unexpected Organocatalyzed Stereoselective Ring Opening of Cyclopropanes

The development of efficient methods for the facile construction of important molecular architectures is a central goal in organic synthesis. An unprecedented organocatalytic asymmetric cascade Michael-alkylation reaction of α,β-unsaturated aldehydes with bromomalonates has been developed. The process, efficiently catalyzed by chiral diphenylprolinol TMS ether in the presence of base 2,6-lutidine, serves as a powerful approach to the preparation of synthetically and biologically important cyclopropanes in high levels of enantio- and diastereoselectivities. Remarkably, the power of the cascade process is fueled by its high efficiency of the production of two new C−C bonds, two new stereogenic centers, and one quaternary carbon center in one single operation, which otherwise is difficult to achieve by traditional strategies. Moreover, the beauty of the cascade process is further underscored by the nature of the product formation depending on the reaction conditions. With the alternation of base from 2,6-lutidine (1.1 equiv), which is effective for the cyclopropanations, to NaOAc (4.0 equiv), the spontaneous ring-opening of cyclopropanes takes place to lead to stereoselective (E) α-substituted malonate α,β-unsaturated aldehydes. A possible reaction mechanism, which involves a Michael-alkylation−retro-Michael pathway, is proposed and verified by experimental studies. This investigation represents the first example of an organocatalyst-promoted ring opening of the cyclopropanes, whereas such reactions have been intensively explored by Lewis acid-based catalysis

Enantioselective Organocatalytic Double Michael Addition Reactions

A novel organocatalytic, enantioselective domino double Michael addition reaction of α,β-unsaturated aldehydes with ethyl 4-mercapto-2-butenoate has been developed. The process is promoted by chiral diphenylprolinol TMS ether to give chiral tetrahydrothiophenes in high to excellent levels of enantioselectivities