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Oxadiazinoisoquinolinones are obtained in the presence of Na2CO3, while (isoquinolinoolinyloxy)acetamides are produced when Cs2CO3 is used as the base.

A novel straightforward method for the synthesis of 2,3-disubstituted imidazo[1,2-a]pyridine derivatives in water as a truly safe and cheap reaction medium was developed. Hence, N-alkyl pyridinium and S-alkyl thiouronium salts were reacted in the presence of NaHCO3 as a mild base in water to produce imidazo[1,2-a]pyridines in moderate to excellent yields.

A novel method for the direct synthesis of 5-arylidene-2-thiohydantoins from thioureas and aromatic aldehydes in the presence of base in ethanol was developed. Application of this efficient method allowed preparing thiohydantoins, which are difficult to synthesis by traditional methods.

A base-promoted domino reaction to synthesize the 2,3-disubstituted indoles from 2-aminobenzaldehyde/2-amino aryl ketones, tosylhydrazine, and aromatic aldehydes has been developed. This strategy provides a simple and beneficial way for the construction of 2,3-disubstituted indole compounds from readily available starting materials under mild conditions.

A series of 1,4-disubstituted 1,2,3-triazoles containing formyl was synthesized from a variety of readily available nitrobenzaldehydes and alkynes via a convenient one-pot, click-SNAr reaction with moderate to excellent yields. The reactions were easily carried out in hexamethyl phosphoramide in the absence of a base at 60 °C.

Novel Si—B activation by acid/base organocatalysis, which leads to a generally efficient silyl transfer to nitroalkenes is developed.

A novel route to heteroaryl phosphonates (III) using a Pd/Ag-catalyst system without addition of a base is described.

A facile synthetic method to access N-dialkylaminomethyl-2H-1,2,3-triazoles has been developed via a novel reaction mode from N-sulfonyl-1,2,3-triazoles by a base induced reaction. Moreover, 4-phenyl-1H-1,2,3-triazoles can also give the same products even in the absence of a base at high temperature.

A novel access to highly functionalized 2-aminonicotinonitriles via efficient annulations of α-keto vinyl azides and α,α-dicyanoalkenes is described. This annulation was achieved via base-mediated ring-openings and intramolecular rearrangements. A possible mechanism is also proposed.

Tetracyclic products are efficiently obtained by application of a base as key of the annulation reactions.

A base-catalyzed divergent reaction of 3-ylideneoxindoles with O-Boc hydroxycarbamates has been developed to provide efficient access to various amidoacrylates and spiroaziridine oxindoles with generally high yields, which should be potentially useful in drug discovery.

The reaction of β-isothiocyanato carbonyl compounds with hydrazine provides 3-aminopyrimidine-2-thione diastereomers along with acyclic isomers, and the former are submitted to a base-promoted cyclization to form 1,2,4-triazepine-3-thiones.

1-Aryl-2-trimethylsilylethynes, prepared in situ via Sonogashira coupling, undergo base promoted homocoupling to form 1,3-butadiynes in moderate yields.

A series of electronically diverse imines were found to readily react with various donor–acceptor cyclopropyl acid chlorides, with complete regioselectivity, to form 1,3-oxazin-4-ones in moderate yields (25–48% over two steps). Select oxazinones underwent a base induced rearrangement to afford the corresponding cycloheptene-fused oxazinones in good yields (up to 70%).

An efficient organocatalytic approach for the synthesis of 1,3-oxathiolanes and 1,3-thiazolidines is reported. In this methodology, conjugated base of nitromethane was employed as a potential organocatalyst to promote cyclization reaction between strained heterocyclic compounds and heterocumulenes at ambient conditions.

A synthetic route for the preparation of unsymmetrically polysubstituted fluorenes was developed through the base-catalyzed one-pot domino reactions of aromatic ortho-dialdehydes with 1,3-dicarbonyl compounds. This protocol provides expeditious access to indene-fused polycyclic aromatic hydrocarbons such as the benzo[b]fluorene and 13H-indeno[1,2-b]anthracene skeletons.

The influence of various parameters including solvent, base and temperature on the reaction between carbazole and epoxides was studied. This led to the development of a regioselective ring-opening ...

A new one-pot route to azabicycles involving the [3,3]-sigmatropic rearrangement of dehydration product from allylic alcohol carbamate and base promoted twofold cyclization was described.

Enantioenriched 1-amino-4-fluoro-1,2-dihydronaphthalene derivatives are accessed via two complementary synthetic strategies. The careful optimization of the reaction conditions required for the elimination step in one route has allowed both the identification of an anchimerically assisted reaction pathway and, more importantly, access to a divergent reaction pathway toward fluorinated 1,3-amino alcohols from a common intermediate just by adjusting the number of equivalents of base used.

The Weinreb amide group and the counter cation of the base are important for the selective C-Cl bond cleavage of (R)-PhSO(NTs)CH2Cl.

A novel protocol to synthesize multisubstituted benzo[b][1,4]oxazepines from N-(2-haloaryl)enaminones has been developed. In this procedure, only 2 equiv. of Cs2CO3 was required. A variety of polysubstituted benzo[b][1,4]oxazepine derivatives were provided in up to 95% yield for 27 examples.

Cyclization of alk-4-ynals with o -diaminobenzene in DMSO under the sequential action of NH 4 Br and base (KOH or K 2 CO 3 ) affords 1-arylmethylidene-2,3-dihydro-1 H -pyrrolo[1,2- a ]benzimidazoles, which are formed selectively as E - or Z -isomers depending on the base used.

Transition-metal and ligand-free method for the hydroboration of terminal alkynes with B 2 pin 2 was reported in LiOt-Bu/toluene/MeOH system under room temperature. Alkylalkynes and arylalkynes reacted efficiently with high regioselectivity.

The reactions afford the required arylamides in an efficient manner under the basic conditions shown.

A mild and efficient method for the chemoselective synthesis of 7-aryloyl-5 H -pyrano[3,2- c :5,6- c ′]diquinoline-6,8(7 H ,9 H )-diones, representing a new class of substituted pyranodiquinolinone derivatives, via the annulation of arylglyoxalmonohydrates with 2,4-dihydroxyquinoline in the presence of catalytic DBU is described. The salient features of this procedure are high chemo- and regioselectivity, short reaction times, good to high yields, easy work-up, and operational simplicity.

The use of the Broensted base, Et3N, along with a catalytic amount of Lewis base, PPh3, leads to the isomerization of chlorovinyl ketones affording 1,3-dienones.

A series of C2 symmetric guanidinium salts are prepared as chiral phase transfer catalysts and applied to the alkylation of a glycinate Schiff′s base and to the epoxidation of some chalcones.

The formation of C(sp)—N or C(sp)—P bonds proceeds in a one-pot manner and does not require transition-metal catalysts.

Based on a tandem oxidation/aldol condensation reaction meso-1,4-tetralinediol is efficiently converted according to the title reaction.

11-Substituted (CN, CO2Et, SO2Ph) indolo[2,3-b]quinolines were obtained in reactions of N-protected (SiMe2t-Bu, CO2t-Bu) indol-3-yl-acetonitrile, -acetate, and -methylsulfone with nitrobenzene derivatives in presence of base and trialkylchlorosilanes.

Both sulfonamides and arylamines are alkylated with alcohols and a novel hemiaminal model is proposed as the possible intermediate.

The reaction of 5-substituted 2-nitrosophenols with bromomethyl aryl ketones and related compounds employing K2CO3 as a base in refluxing THF and DMF at 80 °C, respectively, delivers 2-aroylbenzoxazoles in a single step with yields up to 85%. The new method involves an intermolecular nucleophilic substitution followed by intramolecular 1,2-addition and elimination. It allows an efficient and practical access to 2-aroylbenzoxazoles under transition-metal-free conditions.

The title thiazines are obtained in one-pot from benzothiazolium cations and α-haloketones by ring expansion under ultrasonication.

An interesting conversion of amino-β-lactam guanidines (III) to imidazolones of type (IV) and (V) is described.

A new practical approach for constructing 2-aminobenzo[d][1,3]selenazines by base mediated multicomponent reaction of isocyanides, selenium and amines under metal-free conditions is reported. A series of selenazine derivatives are observed in moderate to excellent yields.

The thermolysis of pyridinol (I) leads to oxazolo[5,4-b]pyridine-2-carbonitrile (II), whilst the treatment with a base gives oxazine (III).

A new transition metal-free method for the preparation of title compounds (III), (V) and (VII) is reported.