Direct syntheses of 4-aryl-1,2,3,4-tetrahydroisoquinolines and 1-aryl-2,3,4,5-tetrahydro-3-benzoazepines via hydroamination of enol carbamates

Route to Functionalized Tetrahydrobenzo[d]azepines via Re2O7-Mediated Intramolecular Friedel-Crafts Reaction

We describe a Re2O7-mediated intramolecular dehydrative Friedel-Crafts reaction for the efficient synthesis of various benzo-fused heterocycles such as benzazepines and benzazocines. This process is characterized by a broad substrate scope, mild reaction conditions, high efficiency, and high atom economy. The potential application of this methodology was exemplified by the facile preparation of a NMDA antagonist as well as a key intermediate en route to SKF 38393.

A ring expansion strategy towards diverse azaheterocycles

The development of innovative strategies for the synthesis of N-heterocyclic compounds is an important topic in organic synthesis. Ring expansion methods to form large N-heterocycles often involve the cycloaddition of strained aza rings with π bonds. However, in some cases such strategies suffer from some limitations owing to the difficulties in controlling the regioselectivity and the accessibility of specific π-bond synthons. Here, we report the development of a general ring expansion strategy that involves a formal cross-dimerization between three-membered aza heterocycles and three- and four-membered-ring ketones through synergistic bimetallic catalysis. These formal cross-dimerizations of two different strained rings are efficient and scalable, and provide a straightforward and broadly applicable means of assembling diverse N-heterocycles, such as 3-benzazepinones, dihydropyridinones and uracils, which are versatile units in numerous drugs and biologically active compounds. Preliminary mechanistic studies revealed that the C-C bond of strained ring ketones is first cleaved by the Pd⁰ species during the reaction.

Substitution-Controlled Selective Formation of Hexahydrobenz[ e]isoindoles and 3-Benzazepines via In(OTf)3-Catalyzed Tandem Annulations

A dramatic N-substituent controlled tandem annulation of 2-(2-(2-bromoethyl)phenyl)-1-sulfonylaziridines with 1,3-dicarbonyl compounds has been developed. When the N-substituent was a 4-methylbenzenesulfonyl group (Ts), sequential ring opening of aziridines, nucleophilic substitution, and lactamization took place to provide a series of hexahydrobenz[ e]isoindole compounds in good yields with good diastereoselectivities. By contrast, 3-benzazepine compounds were afforded in good yields via ring opening of aziridines and nucleophilic substitution when the N-substituent was the 4-nitrobenzenesulfonyl group (Ns).

N-(3-tert-Butyl-1-phenyl-1H-pyrazol-5-yl)-N-(4-methoxybenzyl)acetamide: a hydrogen-bonded chain of centrosymmetric rings

The molecule of the title compound, C(23)H(27)N(3)O(2), adopts a conformation having no internal symmetry so that the compound exhibits conformational chirality. The molecules are linked by a combination of C-H...O and C-H...pi(arene) hydrogen bonds into a chain of rings in which two types of centrosymmetric ring alternate.

Convenient synthesis of amaryllidaceae alkaloid, (+/-) latifine dimethyl ether

A short route for the synthesis of (+/-) latifine dimethyl ether is reported. The key steps involved are Grignard reaction, conversion of alcohol to nitrile using trimethylsilyl cyanide, reduction of the nitrile intermediate followed by Pictet–Spengler cyclisation and reductive N-methylation in a single step to provide latifine dimethyl ether as a racemate.

An efficient synthesis of (+/-) cherylline dimethyl ether

A concise route for the synthesis of (+/-) cherylline dimethyl ether is reported. The key steps involved are Grignard reaction, conversion of alcohol to nitrile using (N-( p-toluene sulfonyl)imidazole and sodium cyanide), reduction of the nitrile intermediate followed by Pictet–Spengler cyclisation and reductive N-methylation in a single step to provide cherylline dimethyl ether as a racemate.