Synthesis of 5-Azaindolizine Derivatives by the Palladium-Catalyzed Intermolecular Formal [3+2] Cycloaddition of Alkylidenecyclopropanes with 1,2-Diazines

Palladium- and Brønsted acid-catalyzed enantio-, site- and E/Z-selective addition of alkylidenecyclopropanes with imines

Transition-metal catalyzed functionalization of ACPs has been widely investigated in cycloaddition and 1,3-difunctionalization reactions. However, the transition metal catalyzed nucleophilic reactions of ACPs have rarely been reported. In this article, an enantio-, site- and E/Z-selective addition of ACPs with imines for the synthesis of dienyl substituted amines has been developed via palladium- and Brønsted acid co-catalysis. A range of synthetically valuable dienyl substituted amines were effectively prepared with good to excellent yields and excellent enantio- and E/Z-selectivities.

Tandem Construction of Indole-Fused Phthalazines from (2-Alkynylbenzylidene)hydrazines under Metal-Free Conditions

An efficient approach to invent diversely substituted indole-fused phthalazines from in situ formed (2-alkynylbenzylidene)hydrazines under metal-free conditions via selective radical cyclization has been developed. Notably, this 6-exo-dig addition-cyclization tandem procedure proceeds under air atmosphere and shows a broad substrate suitability, as well as avoids harmful byproducts, which complies with the concept of green synthesis.

Recent advances in the chemical transformations of functionalized alkylidenecyclopropanes (FACPs)

Classification of functionalized alkylidenecyclopropanes (FACPs) and recent chemical transformations for the synthesis of novel and useful polycyclic and heterocyclic compounds.

Heterocycles from methylenecyclopropanes

The discovery of a series of novel organic reactions has made methylenecyclopropanes (MCPs) some of the most popular building blocks in synthetic organic chemistry during the past two decades. Among reported works, the construction of heterocycles from MCPs has highlighted new synthetic methodologies that afford more opportunities for the quick synthesis of elaborately substituted products, and this should draw a great deal of attention. However, reviews in this area are insufficient, and the latest monograph on heterocycle synthesis from MCPs was published 12 years ago. This review aims to summarize the novel organic reactions of MCPs to produce heterocycles published in recent years, which have provided specific and powerful tools for organic synthesis.

Selectivity in metal-catalyzed carbon-carbon bond cleavage of alkylidenecyclopropanes

When more complex system leads to simpler reactivity profile; the ring-opening of strained three-membered rings such as methylene- and alkylidenecyclopropanes generally lead to several products. If one starts with more functionalized carbon skeletons, selective reactions are now observed and rationalization as well as synthetic applications are described in this concept article. This methodology could be used to the preparation of challenging structural motifs possessing quaternary carbon stereocenters in acyclic systems.

Stereospecific synthesis of alkylidenecyclopropanes via sequential cyclopropene carbomagnesation/1,3-carbon shift

Alkylidenecyclopropanes can be synthesized from enantiomerically enriched cyclopropene derivatives with >99% stereotransfer and good to excellent yield. The protocol comprises the stereoselective reaction of Grignard reagents with 1-alkoxymethyl-3-hydroxymethylcyclopropenes and a stereospecific [1,3] carbon shift reaction.

An expedient and new synthesis of pyrrolo[1,2-b]pyridazine derivatives

The reaction of 2-[2-(4-fluorophenyl)-2-oxo-1-phenylethyl]-4-methyl-3-oxo-pentanoic acid phenylamide with tertiary butyl carbazate and subsequent condensation of the resulting carbamate derivative with a chalcone provided a facile new approach to pyrrolo[1,2-b]pyridazine derivatives.

Synthesis of the indene, THF, and pyrrolidine skeletons by Lewis acid mediated cycloaddition of methylenecyclopropanes with aldehydes, N-tosyl aldimines, and acetals

Methylenecyclopropanes (MCPs 1) react with aldehydes, N-tosyl aldimines, and acetals to give the corresponding indene, THF, and pyrrolidine cycloaddition products in the presence of BF3 x OEt2 under mild reaction conditions. Some special transformations of MCPs 1 with aldehydes have been reported in this paper. A plausible reaction mechanism has been discussed, which is based on a deuterium-labeling experiment and the Prins-type reaction mechanism.

Lewis acid catalyzed ring-opening reactions of methylenecyclopropanes with diphenylphosphine oxide in the presence of sulfur or selenium

Methylenecyclopropanes undergo an interesting Lewis acid-catalyzed ring-opening reaction with diphenylphosphine oxide in the presence of sulfur or selenium upon heating at 85 degrees C in 1,2-dichloroethane to give the corresponding homoallylic thiol or selenol derivatives in good to high yields.

Direct Synthesis of Monofunctionalized Indolizine Derivatives Bearing Alkoxymethyl Substituents at C-3 and Their Benzofused Analogues

[reaction: see text] Treatment of (Z)-2-pyridine and quinoline silylated vinylacetylenes at reflux with several alcohols in the presence of a suitable inorganic base (KOH, K2CO3, CsF, or KF) serendipitously gave 3-alkoxylmethylindolizines and the corresponding 1-alkoxymethylpyrrolo [1,2-a]quinolines and not the anticipated desilylated vinylacetylene derivatives. A mechanistic possibility for this unexpected chemical transformation is suggested.