Direct Catalytic Asymmetric Aminoallylation of Aldehydes: Synergism of Chiral and Nonchiral Brønsted Acids

The development of a catalytic asymmetric method for the direct aminoallylation of aldehydes is described that gives high asymmetric inductions for a broad range of substrates including both aromatic and aliphatic aldehydes. This method allows for direct isolation of unprotected analytically pure homoallylic amines without chromatography. The unique catalyst system developed for this process involves the synergistic interaction between a chiral and a nonchiral Brønsted acid

Trimethylsilyldiazomethane as a Versatile Stitching Agent for the Introduction of Aziridines into Functionalized Organic Molecules

A highly enantioselective route for the introduction of aziridines into functionalized organic molecules was developed via a tandem acylation and aziridination of TMSCHN2

A New Convergent Strategy for the Synthesis of Calixarenes via a Triple Annulation of Fischer Carbene Complexes

A new method for the synthesis of unsymmetrical calix[4]arenes is described which involves the reaction of a diyne with a bis-carbene complex of chromium. This synthesis of calixarenes is unique in that it involves the formation of two of the four benzene rings of the calixarene and the macrocyclic ring of the calixarene in the same step. Thus, two of the four benzene rings of the calixarene are identical, but the other two rings may each be different, giving a general method for the synthesis of calixarenes in which there are either two or three differently substituted benzene rings. This protocol gives access to a large family of unsymmetrical calixarenes by the proper choice of arene substitution in the starting diyne and the starting carbene complex. Nine examples are presented in which the yields in the key triple annulation step range from 22 to 41%. The overall yields of calixarenes from commercially available starting materials compare favorably with those from existing methods for the synthesis of unsymmetrical calix[4]arenes

Moore-Type Cyclization Leading to Arene Chromium Tricarbonyl 1,4-Diradical Intermediates and the Isolation of Indolines

Moore-Type Cyclization Leading to Arene Chromium Tricarbonyl 1,4-Diradical Intermediates and the Isolation of Indoline

Enantioselective Organocatalytic Direct Michael Addition of Nitroalkanes to Nitroalkenes Promoted by a Unique Bifunctional DMAP-Thiourea

Enantioselective Organocatalytic Direct Michael Addition of Nitroalkanes to Nitroalkenes Promoted by a Unique Bifunctional DMAP-Thioure

A New Convergent Strategy for the Synthesis of Calixarenes via a Triple Annulation of Fischer Carbene Complexes

A new method for the synthesis of unsymmetrical calix[4]arenes is described which involves the reaction of a diyne with a bis-carbene complex of chromium. This synthesis of calixarenes is unique in that it involves the formation of two of the four benzene rings of the calixarene and the macrocyclic ring of the calixarene in the same step. Thus, two of the four benzene rings of the calixarene are identical, but the other two rings may each be different, giving a general method for the synthesis of calixarenes in which there are either two or three differently substituted benzene rings. This protocol gives access to a large family of unsymmetrical calixarenes by the proper choice of arene substitution in the starting diyne and the starting carbene complex. Nine examples are presented in which the yields in the key triple annulation step range from 22 to 41%. The overall yields of calixarenes from commercially available starting materials compare favorably with those from existing methods for the synthesis of unsymmetrical calix[4]arenes

A New Convergent Strategy for the Synthesis of Calixarenes via a Triple Annulation of Fischer Carbene Complexes

A new method for the synthesis of unsymmetrical calix[4]arenes is described which involves the reaction of a diyne with a bis-carbene complex of chromium. This synthesis of calixarenes is unique in that it involves the formation of two of the four benzene rings of the calixarene and the macrocyclic ring of the calixarene in the same step. Thus, two of the four benzene rings of the calixarene are identical, but the other two rings may each be different, giving a general method for the synthesis of calixarenes in which there are either two or three differently substituted benzene rings. This protocol gives access to a large family of unsymmetrical calixarenes by the proper choice of arene substitution in the starting diyne and the starting carbene complex. Nine examples are presented in which the yields in the key triple annulation step range from 22 to 41%. The overall yields of calixarenes from commercially available starting materials compare favorably with those from existing methods for the synthesis of unsymmetrical calix[4]arenes

Total Synthesis of Carbazoquinocin C: Application of the <i>o</i>-Benzannulation of Fischer Carbene Complexes to Carbazole-3,4-quinone Alkaloids

The photoinduced o-benzannulation of 3-(2-vinyl)indolylcarbene complexes provides a direct route to carbazole derivatives that are oxygenated in the 3- and 4-positions. This reaction is quite efficient and provides for a unique synthesis of the lipid peroxidation inhibitor carbazoquinocin C

Iron in the Service of Chromium: The <i>ortho</i>-Benzannulation of <i>trans</i>,<i>trans</i>-Dienyl Fischer Carbene Complexes

Chromium Fischer carbene complexes with trans,trans-dienyl substituents on the carbene carbon will react with diiron nonacarbonyl to give 2-alkoxycyclohexa-2,4-dienone iron tricarbonyl complexes and/or 2-alkoxyphenols in excellent yields. In the presence of silica gel or base, the cyclohexadienone complex will suffer loss of the iron and aromatization to give 2-alkoxyphenols. The formation of 2-alkoxyphenols from dienyl chromium carbene complexes is a known process (ortho-benzannulation) that only occurs with certain cis,trans-dienyl complexes. Control experiments show that trans,trans-dienyl chromium carbene complexes do not undergo conversion to 2-alkoxyphenols in the absence of an iron source. The process most likely occurs either via coordination of the dienyl unit in the chromium carbene complex to an iron tricarbonyl group and then loss of the chromium or via direct trans-metalation of the carbene ligand to give an iron carbene complex and then internal coordination to the dienyl unit such that cis to trans isomerization of the α,β-double bond occurs

Macrocyclization of Fischer Carbene Complexes as an Approach to Cyclophanes

Macrocyclization of Fischer Carbene Complexes as an Approach to Cyclophane