FeCl₃‑Promoted [3 + 2] Annulations of γ‑Butyrolactone Fused Cyclopropanes with Heterocumulenes

The [3 + 2] annulations of γ-butyrolactone fused donor–acceptor (D–A) cyclopropanes with aromatic isothiocyanates and dialkyl carbodiimides promoted by FeCl₃ is reported. A series of bicyclic/polycyclic γ-butyrolactone fused thioimidates and γ-butyrolactone fused amidines containing four contiguous stereogenic centers were obtained in excellent yields as single stereoisomers

Lewis Acid-Catalyzed Annulations of Geminally Disubstituted Cyclopropanes with Aldehydes or 1,3,5-Triazinanes

Under the catalysis of simple Lewis acid catalysts, 2-(1-aroylcyclopropyl)malonates demonstrated unique reactivities in annulation reactions with aryl/alkyl aldehydes, paraformaldehyde, and 1,3,5-triazinanes. Three types of structurally diverse cyclic products that are otherwise not easy to obtain were generated in moderate to good yields and excellent diastereoselectivities. Possible reaction pathways leading to these products were proposed on the basis of the results of control experiments

Copper(I)-Catalyzed Kinetic Resolution of <i>N</i>‑Sulfonylaziridines with Indoles: Efficient Construction of Pyrroloindolines

The first Lewis acid catalyzed [3 + 2] annulation of indoles and 2-aryl-<i>N</i>-tosylaziridines was realized by using copper­(I)/chiral diphosphine complexes as a catalyst. With this method, a variety of uniquely substituted chiral pyrroloindolines bearing multiple contiguous stereogenic centers were facilely accessed in a straightforward, high-yielding, and highly stereoselective way under mild conditions

<i>cis</i>-2,3-Disubstituted Cyclopropane 1,1-Diesters in [3 + 2] Annulations with Aldehydes: Highly Diastereoselective Construction of Densely Substituted Tetrahydrofurans

A series of <i>cis</i>-2,3-disubstituted cyclopropane 1,1-diesters were examined in the AlCl₃-promoted [3 + 2]-annulations with aldehydes. In this reaction, these <i>cis</i>-cyclopropanes displayed reactivities starkly different from their <i>trans</i> counterparts in terms of the high chemical yields (up to 98%) and provided the desired annulation products with excellent diastereomeric purity. This protocol provides a facile and highly stereoselective way to construct synthetically useful pentasubstituted tetrahydrofurans not easily accessible using other methods

<i>cis</i>-2,3-Disubstituted Cyclopropane 1,1-Diesters in [3 + 2] Annulations with Aldehydes: Highly Diastereoselective Construction of Densely Substituted Tetrahydrofurans

A series of <i>cis</i>-2,3-disubstituted cyclopropane 1,1-diesters were examined in the AlCl₃-promoted [3 + 2]-annulations with aldehydes. In this reaction, these <i>cis</i>-cyclopropanes displayed reactivities starkly different from their <i>trans</i> counterparts in terms of the high chemical yields (up to 98%) and provided the desired annulation products with excellent diastereomeric purity. This protocol provides a facile and highly stereoselective way to construct synthetically useful pentasubstituted tetrahydrofurans not easily accessible using other methods

Synthesis, Characterization, and Reactivity of Lanthanide Amides Incorporating Neutral Pyrrole Ligand. Isolation and Characterization of Active Catalyst for Cyanosilylation of Ketones

A series of lanthanide amido complexes incorporating a neutral pyrrole ligand were synthesized and characterized, and their catalytic activities were studied. Treatment of [(Me₃Si)₂N]₃­Ln­(μ-Cl)­Li­(THF)₃ with 1 equiv of [(2,5-Me₂C₄H₂N)­CH₂CH₂] ₂NH (<b>1</b>) in toluene afforded the corresponding lanthanide amides with the formula [η⁵:η¹-(2,5-Me₂C₄H₂N)­CH₂CH₂]₂­NLn­[N­(SiMe₃)₂]₂ (Ln = La (<b>2</b>), Nd (<b>3</b>)). Reaction of <b>2</b> or <b>3</b> with <i>N</i>,<i>N</i>′-dicyclo­hexyl­carbo­diimide (CyNCNCy) gave the carbodiimide selectively inserted into the appended Ln–N bond products formulated as CyNC­{[<i>N</i>,<i>N</i>-(2,5-Me₂C₄H₂N)­CH₂CH₂]₂N}­NCyLn­[N­(SiMe₃)₂]₂ (Ln = La (<b>4</b>), Nd (<b>5</b>)). Reactions of the lanthanide amides with Me₃SiCN were also examined. A mixed reaction of [(Me₃Si)₂N]₃­La­(μ-Cl)­Li­(THF)₃, [(2,5-Me₂C₄H₂N)­CH₂CH₂]₂NH (<b>1</b>), and Me₃SiCN in toluene at room temperature produced the novel cyano bridged dinuclear lanthanum complex η⁵:η¹:η³-[(2,5- Me₂C₄H₂N­CH₂CH₂)₂N]­La­[N­(SiMe₃)₂]­(μ-CN)­La­[N­(SiMe₃)₂]₃ (<b>6</b>). The stoichiometric reactions of lanthanide amides <b>2</b> or <b>3</b> with Me₃SiCN produced the novel trinuclear lanthanum and neodymium complexes {(η⁵:η¹-[(2,5-Me₂C₄H₂­NCH₂CH₂)₂N]­Ln­[N­(SiMe₃)₂]­(μ-CN)}₃ (Ln = La (<b>7</b>), Nd (<b>8</b>)) through selective σ-bond metathesis reaction of the terminal Ln–N (N­(SiMe₃)₂) bond with the Si–C bond of Me₃SiCN. On the basis of the stoichiometric reactions of complexes <b>2</b>, or <b>3</b> with Me₃SiCN, complexes <b>2</b>, <b>3</b>, <b>4</b>, <b>5</b>, <b>7</b>, and <b>8</b> as catalysts for cyanosilylation of ketones were investigated. Results indicated that these complexes displayed a high catalytic activity on addition of Me₃SiCN to ketones, and the activity of the complexes has the order of <b>7</b> ∼ <b>8</b> > <b>2</b> ∼ <b>3</b> ∼ <b>4 ∼ <b>5</b></b>. Thus, complex <b>7</b> or <b>8</b> was proposed as the active catalyst in the catalytic reaction for the precatalysts of <b>2</b> and <b>3</b>