Concise synthesis of aromatic tertiary amines via a double Petasis–borono Mannich reaction of aromatic amines,formaldehyde, and organoboronic acids

A simple and efficient strategy to construct aromatic tertiary amines via a double Petasis–borono Mannich reaction of aromatic amines, formaldehyde, and organoboronic acids has been developed. The transformation provides a useful method for the synthesis of amine derivatives.     

A concise synthesis of a β-lactamase inhibitor

MK-7655 (1) is a β-lactamase inhibitor in clinical trials as a combination therapy for the treatment of bacterial infection resistant to β-lactam antibiotics. Its unusual structural challenges have inspired a rapid synthesis featuring an iridium-catalyzed N-H insertion and a series of late stage transformations designed around the reactivity of the labile bicyclo[3.2.1]urea at the core of the target.     

Brønsted acid catalyzed cyclization of hydroxylated enynes: a concise synthesis of five-membered heterocycles

A mild and direct pathway for the formation of five‐membered heterocyclic compounds from hydroxylated enynes has been developed. In this reaction, hydroxylated enynes were selectively transformed into five‐membered heterocyclic compounds 2 , with an allene moiety at the 3‐position, in the presence of F₃CSO₃H (0.1 mol %). When R¹, R²=Ph, diphenylvinyl‐2,3‐dihydro‐1H‐pyrrole ( 2 y ) was obtained. With HSbF₆ (5 mol %) as the catalyst, polycyclic skeletons 3 and 4 with adjacent stereocenters were obtained. When R¹=H and R²=styrene, 1,3‐dienyl‐2,5‐dihydro‐1H‐pyrrole ( 6 as ) was formed. This Brønsted acid catalyzed domino process involves the formation of an allene carbocation intermediate, which can be readily trapped by olefins to give various novel five‐membered heterocyclic skeletons.     

A facile synthesis of γ-butenolides via cyclization of 3-alkenoic acids with dimethyl sulfoxide and oxalyl bromide

The combination of dimethyl sulfoxide and oxalyl bromide was used to accomplish the cyclization of 3-alkenoic acids with the aid of a base to afford γ-butenolides, in which bromodimethylsulfonium salt generated in situ was proposed to serve as a Br⁺ source.     

Total synthesis of amorfrutin A via a palladium-catalyzed migratory prenylation–aromatization sequence

The total synthesis of amorfrutin A, a prenyl bibenzyl natural product has been achieved in five steps from 2,2,6-trimethyl-4H-1,3-dioxin-4-one. The key step of the synthesis is an efficient palladium(0)-catalyzed decarboxylative prenylation migration and aromatization sequence.     

A new concise stereoselective method for the preparation of a β-hydroxyfurfurylamine derivative and synthesis of 1-deoxyazasugar isomers

A new method to prepare a chiral building block, a β-hydroxyfurfurylamine derivative, is achieved and 1-deoxyazasugar isomers are synthesized.     

Novel synthesis of tetrahydro-1H-pyrrolo[1,2-a]imidazol-2-ones via decarboxylative cyclization reaction of α-amino acids and α-ketoamides

An efficient and practical method was developed for the synthesis of tetrahydro-1H-pyrrolo[1,2-a]imidazol-2-ones based on the decarboxylative cyclization reaction of α-ketoamides and proline. In most cases, tetrahydro-1H-pyrrolo[1,2-a]imidazol-2-ones were obtained with perfect diastereoselectivity to give trans-isomer in excellent yield.     

A versatile enantioselective synthesis of azabicyclic ring systems: a concise total synthesis of (+)-grandisine D and unnatural analogues

Closing in on azacines: We have developed a new six step approach for the rapid and enantioselective synthesis of indolizidine, pyrrolo[1,2-a]azepine, and pyrrolo[1,2-a]azocine azabicyclic systems and their respective lactam congeners, which are found in a host of natural products as well as pharmaceutical preparations. This protocol enables a concise enantioselective total synthesis of (+)-grandisine?D in 16.4?% overall yield from commercial materials (see scheme).     

Formal total synthesis of (±)-bisabolangelone by using a radical cyclization

A photoreductive cyclization has been used to synthetize the bicyclic core of (±)-bisabolangelone.     

Straightforward and highly efficient catalyst-free regioselective reaction of thiol to β-nitrostyrene: a concise synthesis of vinyl sulfide and nitro sulfide

Under catalyst-free reaction conditions, solvent-mediated addition of thiol 2 to β-nitrostyrene 1 proceeded with regioselective control to afford either adduct 3 or vinyl sulfide 4 in good to excellent yield. Thermodynamic and autocatalytic reaction mechanisms were proposed to rationalize the products thus formed.     

Stereospecific synthesis of syn-α-oximinoamides by a three-component reaction of isocyanides, syn-chlorooximes, and carboxylic acids

A stereospecific multicomponent reaction among isocyanides, syn-chlorooximes, and carboxylic acids provides an efficient synthesis of biologically relevant syn-α-oximinoamides.     

Efficient synthesis of 3-arylbutadiene sulfones using the Heck–Matsuda reaction

An efficient and practical method for a scalable synthesis of 3-arylbutadiene sulfones deals with the ligand-free Heck–Matsuda reaction of sulfolene with aryldiazonium tetrafluoroborates followed by triethylamine-promoted double bond shift.     

Semmler–Wolff aromatisation: a concise route for the synthesis of 5-amino-quinazolines and 4-amino-indoles

A simple and efficient methodology for the synthesis of 5-amino-quinazolines and 4-amino-indoles via Semmler–Wolff aromatisation reaction has been carried out. The oximation of keto intermediates followed by Semmler–Wolff aromatisation using acetic anhydride and a catalytic amount of sodium iodide in xylene provided the desired quinazolines and indoles.     

Enantioselective formal synthesis of (−)-aurantioclavine using Pd-catalyzed cascade cyclization and organocatalytic asymmetric aziridination

The enantioselective formal synthesis of (?)-aurantioclavine is described. The core tricyclic skeleton was synthesized using a Pd-catalyzed Heck insertion–allylic amination cascade. The stereocenter was constructed by a highly enantioselective organocatalytic asymmetric aziridination reaction.     

A common strategy for the synthesis of (+)-gabosine N, (+)-gabosine O,and some carbapyranoses using a Nozaki–Hiyama–Kishi reaction and RCM

Stereoselective synthesis of carbasugars (+)-gabosine N 1 and (+)-gabosine O 2, carba-α-l-rhamnose 17, and carba-6-deoxy-α-l-talose 18 by using a Nozaki–Hiyama–Kishi (NHK) reaction and ring-closing metathesis.     

Naturally occurring organic acids for organocatalytic synthesis of pyrroles via Paal–Knorr reaction

Research on Chemical Intermediates - In this study, common naturally occurring organic acids, namely oxalic, malonic, succinic, tartaric and citric acid (as safe, inexpensive, and biodegradable...     

A concise synthesis of Ni-didecarboxysirohydrochlorin hexamethylester—a model compound for key intermediates in heme d1 and heme biosynthesis

An efficient synthesis of Ni-didecarboxysirohydrochlorin hexamethylester rac-13 was achieved by Barton olefination starting from a readily available dioxo-isobacteriochlorin rac-9. The synthetic route should open a general facile access to this type of naturally occurring hydroporphyrins. Isobacteriochlorins 3–6 are key intermediates in heme d₁ and heme biosynthesis of sulfate reducing and denitrifying bacteria as well as in archaebacteria.