Palladium mediated stereospecific synthesis of 3-enynyl substituted thioflavones/flavones

The stereocontrolled synthesis of enynes has been accomplished via a sequential Heck-Sonogashira reaction in a simple synthetic operation. A variety of terminal alkynes were reacted with 3-iodo(thio)flavone in the presence of a palladium catalyst and a copper salt affording a mild and one-pot method for the first synthesis of the corresponding 3-enynyl and/or alkynyl derivatives. The mechanism and scope of the reaction are discussed.     

Regio- and stereospecific synthesis of allylic tertiary amines

E and Z allylic amines have been synthesised by stereo-specific elimination of Ph₂PO₂^? from pure diastereoisomers (3) and (4).     

Regio- and stereospecific synthesis of beta-sulfonamidodisulfides and beta-sulfonamidosulfides from aziridines using tetrathiomolybdate as a sulfur transfer reagent

A comprehensive study of a general and effective one-step procedure for the synthesis of beta-sulfonamidodisulfides directly from N-tosyl aziridines in a regio- and stereospecific manner under neutral conditions without the use of any Lewis acid or base has been reported. This methodology is extended to the synthesis of an optically pure cyclic seven-membered disulfide 29. Synthesis of a variety of beta-sulfonamidosulfides involving tandem, multistep reactions in one pot is also reported.     

Pd-catalyzed copper-free carbonylative Sonogashira reaction of aryl iodides with alkynes for the synthesis of alkynyl ketones and flavones by using water as a solvent

The Pd-catalyzed copper-free carbonylative Sonogashira coupling reaction to synthesize alkynyl ketones from terminal alkynes and aryl iodides was achieved by using water as a solvent. The reaction was carried out at room temperature under balloon pressure of CO with Et(3)N as a base. The developed method was successfully applied to the synthesis of flavones.     

De novo synthesis of oligosaccharides using a palladium-catalyzed glycosylation reaction

The natural all d- and/or unnatural all l-1,4- and 1,6-oligosaccharides were synthesized from furan alcohols using a palladium-catalyzed glycosylation reaction. The 1,4- and 1,6-alpha-manno-disaccharides were achieved in seven total steps starting from chiral furan alcohols. Similarly, 1,4- and 1,6-alpha-manno-trisaccharides were also synthesized in nine total steps. Key to the overall efficiency of this process was the use of highly diastereoselective palladium-catalyzed glycosylations, reductions, and dihydroxylations.     

A copper-free Sonogashira reaction using a Pd/MgLa mixed oxide

A new Pd/MgLa mixed oxide is found to be an efficient catalyst for the Sonogashira reaction of aryl iodides, bromides and even activated chlorides in the absence of a copper salt.     

A novel palladium-catalyzed arylation-dehydroaromatization reaction: synthesis of 7-aryltetralones

A new one-pot room-temperature palladium-catalyzed synthesis of 7-aryltetralones was discovered. This tandem process includes a palladium-catalyzed gamma-selective arylation of the enone 4 followed by a dehydrogenation-aromatization of the initial cross-coupling product. [reaction: see text]     

A novel and stereospecific synthesis of (+)-exo-brevicomin

A novel and stereospecific synthesis of (+)-exo-brevicomin is disclosed. The key step of the reaction sequence employs the sulfinyl moiety as an intramolecular nucleophile to functionalize an alkene π-complexed to a bromonium ion.     

A novel synthesis of 2-aryl-2H-indazoles via a palladium-catalyzed intramolecular amination reaction

[reaction: see text] A variety of 2-aryl-2H-indazoles were synthesized by the palladium-catalyzed intramolecular amination of the corresponding N-aryl-N(o-bromobenzyl)hydrazines. Of several sets of reaction conditions surveyed, the combination of Pd(OAc)2/dppf/tBuONa gave the best results. This method applies to a wide scope of substrates containing electron-donating and electron-withdrawing substituents.     

Regio- and stereoselective synthesis of novel tetraspiro-bispyrrolidine and bisoxindolopyrrolidine derivatives through 1,3-dipolar cycloaddition reaction

An efficient approach to the synthesis of a new class of tetraspiro-bispyrrolidines and tetraspiro-bisoxindolopyrrolidines has been accomplished through 1.3-dipolar cycloaddition reaction. The reported method is a one-pot, three component reaction, that is, run under solvent-free microwave conditions.     

Regio- and stereospecific addition of phosphines to cyanoacetylenes

Primary and secondary phosphines add regio- and stereospecifically to phenylcyanoacetylene and 4-hydroxy-4-methylpent-2-ynenitrile under mild conditions to form corresponding functionalized secondary and tertiary phosphines of Z-configuration in 70-91% yield. According to ESR and UV data, the addition of primary phosphines to phenylcyanoacetylene involves a single electron transfer process.     

Regio- and stereospecific synthesis of dl-4,5-dibromo-4,5-dideoxy-3,6-O-methyl-chiro-inositol

The regio- and stereospecific synthesis of dl-4,5-dibromo-4,5-dideoxy-3,6-O-methyl-chiro-inositol is reported. Bromination of p-benzoquinone followed by reduction of the carbonyl groups with NaBH₄ gave the corresponding trans-dibromodiol compound, which was reacted with sodium methoxide to produce dimethoxy conduritol-B. Regiospecific bromination of the alkene moiety furnished the desired chiro-inositol derivative.     

The first chemical synthesis of boronic acid-modified DNA through a copper-free click reaction

The first chemical incorporation of the boronic acid group into DNA using a copper-free click reagent was reported. Compared with the PCR-based method, this approach allows for site-specific incorporation and synthesis on a larger scale.     

A novel and stereospecific synthesis of (+)-preussin

A novel and stereospecific approach to (+)-preussin that would permit the synthesis of analogs for structure activity relationship studies, is disclosed. The key step includes the regio- and stereoselective elaboration of a bromohydrin via intramolecular sulfinyl group participation.     

Regio- and stereospecific synthesis of vinyl halides via carbozincation of acetylenic sulfones followed by halogenation

Polysubstituted vinyl halides can be constructed regio- and stereospecifically by treatment of acetylenic sulfones with organozinc reagents in tetrahydrofuran followed by halogenation.     

Regio- and stereoselective synthesis of novel (E)-1-alkenyl carbamate via carbocupration reaction

The stereoselective carbocupration and copper-catalyzed carbomagnesiation reactions of alkynyl carbamates are described as a new and straightforward method for the preparation of (E)-alkenyl enol carbamates. [reaction: see text]     

One-pot palladium-catalyzed synthesis of functionalized 10H-pyrido[1,2-a]quinoxalin-10-ones under copper-free conditions

Reactions of 3-substituted-2-chloroquinoxalines, terminal alkynes, and 1,3-dicarbonyl compounds in the presence of palladium catalyst afforded a number of 6,8,9-trisubstituted-10H-pyrido[1,2-a]quinoxalin-10-ones in 60–86% reaction yields. This one-pot protocol provided an efficient, practical, and direct method for the synthesis of pyrido[1,2-a]quinoxalines from readily available starting materials in the absence of a copper salt.