A concise, diastereoselective total synthesis of (±)-cortistatin J has been completed in 20 steps from furan. Key steps include an intramolecular [4 + 3] cyclization of a disubstituted furan with a (Z)-2-(trialkylsilyloxy)-2-enal to construct the tetracyclic core and a (Z)-vinylsilane/iminium ion cyclization to form the A ring.

The selective ε-functionalization of 5-substituted furfurals via trienamine intermediates is reported herein. This methodology was successfully applied to several 5-substituted furfurals with different amines via formation of a trienamine through the furan ring. The rationalized reaction mechanism involves the addition of the trienamine intermediate to its corresponding iminium-ion producing ne...

A convenient synthesis of 2,4-unsubstituted quinoline-3-carboxylic acid ethyl esters via a domino process is described. The synthesis employs arylmethyl azides as the precursor which undergoes an acid-promoted rearrangement to give an N-aryl iminium ion. Following the addition with ethyl 3-ethoxyacrylate, intramolecular electrophilic aromatic substitution, elimination and subsequent oxidation, ...

The development of enantioselective, copper-catalyzed alkynylations of cyclic iminium and oxocarbenium ions is reviewed. The use of chiral copper-based catalysts has enabled high yields and enantioselectivites in the formation of nitrogen- and oxygen-containing heterocycles with α-stereogenic centers. This review highlights both the accomplishments and the future work needed in this important a...

Iminium ions generated in situ via copper(I) bromide catalyzed oxidation of N-aryl amines readily undergo [4 + 2] cycloadditions with a range of dienophiles. This method involves the functionalization of both a C(sp(3))-H and a C(sp(2))-H bond and enables the rapid construction of polycyclic amines under relatively mild conditions.

The title compound, C(6)H(10)N(2)O, is a zwitterionic pyrazole derivative. The crystal packing is predominantly governed by a three-center iminium-amine N(+)-H⋯O(-)⋯H-N inter-action, leading to an undulating sheet-like structure lying parallel to (100).

We report herein the efficiency of quaternary ammonium salts as co-catalysts in organocatalytic Michael reactions involving iminium activation of α,β-unsaturated aldehydes. The enantioselective formal benzylation of these substrates has been optimized and used to rationalize the role of the ammonium salts in these processes.

A Michael addition/iminium ion cyclization cascade of enones with tryptamine-derived ureas under BINOL phosphoric acid (BPA) catalysis is reported. The cascade reaction tolerates a wide variety of easily synthesized tryptamine-derived ureas, including those bearing substituents on the distal nitrogen atom of the urea moiety, affording polyheterocyclic products in good yields and good to excelle...

The β-amino acid antibiotic (+)-negamycin has been synthesised in ten steps from epichlorohydrin via Sakurai allylation of an isoxazolidine intermediate. The key allylation reaction proceeded with complete trans-selectivity, which is attributed to electrostatic attraction between the chlorine atom and the iminium ion in the Sakurai intermediate.