Significant acceleration of 6 pi-azaelectrocyclization resulting from a remarkable substituent effect and formal synthesis of the ocular age pigment A2-E by a new method for substituted pyridine synthesis

The remarkable acceleration of 6 pi-azaelectrocyclization due to the combination of the C4-carbonyl and the C6-alkenyl or phenyl substituents in 1-azatrienes was found. This observation was rationalized by considering the remarkable orbital interaction between the HOMO and LUMO of 1-azatrienes, which were obtained by molecular orbital calculations. The formal synthesis of the unusual retinal metabolite, A2-E, was achieved by two types of the new one-pot synthesis of substituted pyridines by utilizing the obtained facile 6 pi-azaelectrocyclization, one of which is compatible with the proposed metabolic pathway of A2-E.     

A new pyridine synthesis from conjugated acetylenes and substituted methylamines

Conjugated acetylenes RCCCCR react with substituted methylamines R′CH₂NH₂ at 145–180° to produce corresponding pyridines and/or the corresponding pyridine N-oxides when the reaction is carried out in the presence of air or dimethylsulfoxide. For R = Ph and R′ = cyclo C₆H₁₁, n C₈H₁₇ and PhCH₂, 2,5-diphenylpyridine was also formed, in the last case as the dominant product. For R = PhOCH₂ and R′ = Ph, equivalent amounts of 2-phenyl-3-methyl-6-phenoxymethylpyridine and 2-phenyl-3-phenoxymethyl-6-methylpyridine were formed together with phenol. These results indicate formation of dihydropyridines and their oxidation via radical intermediates.     

A new effective route for the synthesis of substituted 2h-indazoles

A two-stage synthesis of 2H-indazoles has been established, based on consecutive reactions of reduction of 2-alkyl-, 2-cyclopropyl-, and 2-arylcarbonylazobenzenes to phenylazo-substituted benzyl alcohols and intramolecular heterocyclization of the reduction products under the influence of organic acids.     

A new synthesis of substituted spiro butyrolactones via dyotropic rearrangement

Spiro butyrolactones bearing various α-substituents have been synthesized in three steps from acetic acid derivatives; the sequence employs a dyotropic rearrangement as its pivotal step.     

A novel synthesis for new substituted imidazoles

The addition of dimethyl acethylendicarboxylate (DMAD) to thiosemicarbazone and guanylhydrazone of aldehydes afforded compoundes which were characterized to be new substituted imidazoles. Their structures were determined by ¹H NMR, IR, mass spectra and elemental analyses.     

A convenient method for the synthesis of substituted thioureas

A convenient method for the synthesis of substituted thioureas by the reaction of primary amines with molybdenum dialkyl dithiocarbamates has been developed. Primary amines on reaction with 0.5 equiv of molybdenum xanthate produce the corresponding thioureas in moderate to good yields in short times. Similar reactions with propargylamine or 2-aminoethanol produce cyclic thiaoxazolidine and oxazolidine derivatives, respectively.     

A new synthesis of angulary substituted octalins via an anionic oxy-cope rearrangement

The divinyl carbinols $\text{3a}$ and $\text{3b}$ furnished octalinols $\text{4a}$ and $\text{4b}$ respectively on treatment with base.     

Synthesis of substituted 4-pyridones and 4-aminopyridinium salts via a one-pot pyridine synthesis

Synthesis of substituted 4-benzyloxypyridinium salts by the addition of Grignard reagents to pyridine N-oxides provides an efficient route for obtaining substituted 4-pyridones or 4-aminopyridinium salts.     

A new catalytic method for the synthesis of selectively substituted biphenyls containing an oxoalkyl chain

A novel reaction sequence leading to the synthesis of substituted biphenyls containing a carbonyl group in an aliphatic chain has been achieved in one-pot reaction starting from iodoarenes and allylic alcohols under the catalytic action of palladium and norbornene. The latter is temporarily incorporated into a palladacycle, which directs the reaction towards the selective formation of an arylaryl bond. Norbornene spontaneously deinserts to allow the biphenylylpalladium bond thus formed to react in its turn with the allylic alcohol.     

A method for the parallel synthesis of multiply substituted oxazolidinones

There are many examples of both naturally occurring and synthetic molecules containing a 2-oxazolidinone ring that have significant biological activity. The oxazolidinone ring potentially has three sites for attachment of diversity elements. A synthesis that can provide for inclusion of diversity elements at all three positions should be a powerful method for the preparation of oxazolidinone libraries. In this paper we present the preparation of a 3 x 3 x 3 array yielding 27 different products with minimal workup, high yields, and, most importantly, high purity. Using an intramolecular acylnitrene-mediated aziridination reaction, we have prepared (triphenylmethoxymethyl)-3-oxa-1-azabicyclo[3.1.0]hexan-2-one as a starting material for library generation. The first substitution involves opening the aziridine ring of the azabicyclo[3.1.0]hexane ring system using a Grignard reagent. The nitrogen of the oxazolidinone is now ready for substitution via alkylation or arylation. Removing the trityl protecting group via esterification under mildly acidic conditions accomplishes the final substitution.     

A facile method for the synthesis of substituted 2-ylidene-1,3-oxathioles from acetophenones

Compounds incorporating 1,3-oxathiole moieties in their frameworks are biologically active. Active methylene ketones can be easily converted to the corresponding dithiocarboxylates by treatment with trithiocarbonate in the presence of sodium hydride. The reactions of aroyl dithiocarboxylates with α-haloketones such as phenacyl bromide or bromoacetone afford substituted 2-ylidene-1,3-oxathioles in good yields.     

A new method for the synthesis of Z-enediones via IBX-mediated oxidative rearrangement of 2-alkynyl alcohol systems

o-Iodoxybenzoic acid (IBX) was found to mediate the conversion of alpha-alkynyl alcohols into Z-enediones under notably mild conditions via a novel rearrangement mechanism (33-65% yield, 13 examples).     

A new method for the synthesis of 2-phenylsulfonylaziridines via the reaction of α-halosulfonyl carbanion to imines

The reaction of lithio α-chloromethyl phenyl sulfone with imines gave aziridines in good yields. The resulting aziridines were alkylated and underwent the 1,3-dipolar cycloaddition with dimethylacetylene dicarboxylate to give pyrroles in excellent yields.     

A convenient and efficient method for the synthesis of new 2-(4-amino substituted benzilidine) indanone derivatives

An efficient and improved process for the synthesis of novel 1-indanones derivatives has been developed. In the first step of the presented new process, 4-bromobenzaldehyde reacts with 5, 6-dimethoxy-2, 3-dihydro-1H-inden-1-one by N-arylation of corresponding compounds with a variety of aliphatic and aromatic amines to produce a novel category of 1-indanones as the final step. Comparison of this newly designed method with conventional methods show that our method is much more efficient in producing a higher total yield. This innovative synthesis methodology offers several advantages, among which the consumption of inexpensive reagents and the resulting higher total yields of final products are of its remarkable points.     

Novel cyclization reactions of mono- and dichloroazodienes. A new synthesis of substituted pyridazines

Cyclization of the in—situ generated chloroazodienes with a variety of enamines was found to give chloro-substituted tetrahydropyridazines which could be aromatized to pyridazines by base treatment. This sequence appears to be a formal 4 + 2 hetero Diels-Alder reaction with a high degree of regio and stereo control and constitutes a new synthesis of substituted pyridazines. However, cyclization of the corresponding dichloroazodienes with acyclic enamines gave not only the expected pyridazine product, but also gave an N-aminopyrrole product. Combination of the dichloroazodiene with cyclic enamines gave bicyclic dihy-dropyridazines, bicyclic pyridazines, and acyclic enamines which could be forced to close to the bicyclic dihydropyridazines upon further heating. These results would indicate a stepwise mechanism. The scope and mechanistic speculations on these reactions will be presented. While exploring the novel cyclization reactions of 4-chloroazodienes with electron rich olefins we developed a new and general synthesis of substituted 3-phenypyridazines. A number of these analogs were found to exhibit bleaching herbicidal activity (phytoene desaturase inhibition). Further methodology development coupled with analog synthesis led to the preparation of 3-heteroaryloxy and 3-aryloxypyridazines with increased unit activity and selectivity as well as good environmental properties. These compounds were found to be more active than current commercial standards on a number of important weed species with selectivity in corn in the US and small grains in Europe. Greenhouse activity of the most active analogs ranged from 17–140 g/hectare on important narrow-leaf species.     

A new synthesis of substituted 2(1H)-pyrazinones

The hydrohalides of 2-sec-aminoalkanenitriles on treatment with oxalyl halides in o-dichlorobenzene at 80-100° give 3, 5-dihalo-2(1H)-pyrazinones, of which the 3-halo substituent is easily replaced by nucleophiles. A reaction mechanism for the pyrazinone synthesis is proposed.     

A new synthesis of unsymmetrically substituted halophosphines

Chiral, racemic alkylaryl-, or diarylhalophosphines have been obtained in 50–70% yields by treatment of alkylaryl- or diaryl-methylthiohalophosphonium triflates with triphenylphosphine in methylene chloride solution at room temperature or under reflux.     

A new synthesis of substituted 1,4,5,6-tetrahydropyridines

3-Ethoxycarbonyl- and 3-acetyl-4-cyano-2,4, 6, 6-tetramethyl-1, 4, 5, 6-tetrahydropyridines have been obtained by the reaction of diacetoneamine with acetoacetic ester (or acetylacetone), the conversion of the amino ketones so obtained into the corresponding cyanohydrins, and the cyclization of the latter under the influence of alkali.