The first catalytic,asymmetric alpha-additions of isocyanides. Lewis-base-catalyzed,enantioselective Passerini-type reactions

The first, catalytic, enantioselective alpha-additions of isocyanides to aldehydes have been demonstrated (Passerini-type reactions). The catalytic system of silicon tetrachloride and a chiral bisphosphoramide 5a provided high yields and good to excellent enantioselectivities for the addition of tert-butyl isocyanide to a wide range of aldehydes (aromatic, olefinic, acetylenic, aliphatic). Aqueous workup afforded the alpha-hydroxy tert-butyl amides, whereas methanolic quench followed by basic workup afforded the alpha-hydroxy methyl esters.     

Lewis base catalyzed enantioselective aldol addition of acetaldehyde-derived silyl enol ether to aldehydes

[reaction: see text] Chiral phosphoramide catalyzed-enantioselective aldol addition of an acetaldehyde-derived trialkylsilyl enol ether to aromatic aldehydes provides protected aldol products in good yields with good to excellent enantioselectivities. Preliminary studies show that the aldolization intermediate (a chlorohydrin adduct) can be trapped with tert-butyl isocyanide to form an alpha-hydroxy lactone with good selectivity in a single-pot operation.     

Investigation of the one-pot synthesis of quinolin-2-(1H)-ones and the discovery of a variation of the three-component Ugi reaction

Rapid access to the quinolin-2-(1H)-one scaffold is afforded by a sequential 4 component Ugi–Knoevenagel condensation of an aminophenylketone, an aromatic aldehyde possessing electron donating moieties, cyanoacetic acid and an aliphatic isocyanide, in moderate to good yields (49–71%). Interestingly, when the reaction is performed using aromatic aldehydes bearing electron withdrawing moieties or isocyanides containing aromatic or ester units, a mixture of a quinolin-2-(1H)-one and an α-amino amide (Ugi three-component adduct) is afforded in varying ratios. Further when the reaction is performed utilizing a combination of an isocyanide-containing aromatic or carbonyl unit, and an aldehyde possessing an electron withdrawing functionality, the Ugi three-component adduct is exclusively afforded. In our hands this new variation of the Ugi 3CR proved to be efficient and robust affording analogues in good yields (51–70%).     

A One‐Pot O‐Phosphinative Passerini/Pudovik Reaction: Efficient Synthesis of Highly Functionalized α‐(Phosphinyloxy)amide Derivatives

A one‐pot O‐phosphinative Passerini/Pudovik reaction has been developed, based on reacting aldehydes, isocyanides, and phosphinic acids followed by the addition of second aldehydes to form the corresponding α‐(phosphinyloxy)amide derivatives. This is the first reported instance of a Passerini‐type, isocyanide‐based multicomponent reaction using a phosphinic acid instead of a carboxylic acid. The nucleophilicity of the phosphinate group allows a subsequent catalytic Pudovik‐type reaction, affording the highly functionalized α‐(phosphinyloxy)amide derivative in high yield. A wide range of aldehydes and isocyanides are applicable to this reaction.     

Borinic acid catalyzed α-addition to isocyanide with aldehyde and water

A first example of diphenylborinic acid catalyzed α-addition to isocyanide with aldehyde and water is described. The reaction proceeded smoothly in the presence of water and 5 mol % of borinic acid to give the corresponding α-hydroxyamides in good to high yields. A wide range of aldehydes and isocyanides are applicable to this reaction.     

Multicomponent reactions involving zwitterionic intermediates for the construction of heterocyclic systems: one pot synthesis of aminofurans and iminolactones

The reaction of 1:1 zwitterionic intermediate generated in situ from dimethyl acetylenedicarboxylate (DMAD) and cyclohexyl isocyanide with aldehydes and quinones is described. The reaction of stoichiometric amounts of DMAD, isocyanide and aldehydes afforded 2-aminofurans in good yields, while the reaction with quinones gave iminolactones.     

Multicomponent synthesis of 2-imidazolines

[reaction: see text] A multicomponent reaction (MCR) between amines, aldehydes, and isocyanides bearing an acidic alpha-proton gives easy access to a diverse range of highly substituted 2-imidazolines. The limitations of the methodology seem to be determined by the reactivity of the isocyanide and by the steric bulk on the in situ generated imine rather than by the presence of additional functional groups on the imine. Less reactive isocyanides, for example p-nitrobenzyl isocyanide 25a, react successfully with amines and aldehydes, using a catalytic amount of silver(I) acetate. Some of the resulting p-nitrophenyl-substituted 2-imidazolines undergo air oxidation to the corresponding imidazoles. Differences in reactivity of the employed isocyanides are explained with use of DFT calculations. Difficult reactions with ketones instead of aldehydes as the oxo-compound in this MCR are promoted by silver(I) acetate as well.     

Catalytic enantioselective Pudovik reaction of aldehydes and aldimines with tethered bis(8-quinolinato) (TBOx) aluminum complex

New chiral tethered bis(8-quinolinolato) (TBOx) aluminum(III) complexes effectively catalyze the addition of phosphites to aldehydes and aldimines to give enantioenriched alpha-hydroxy and alpha-amino phosphonates in high yields and enantioselectivities with unprecedented reactivity (TON =100 as high as 200). The catalyst is optimized with the low catalyst loading of 0.5 - 1.0 mol %. The modular synthesis of the catalyst allows for potential to tune the reaction for maximum catalytic activity. To date there are few examples with broad substrate scopes that can catalyze both aldehydes and aldimines with such high selectivity and no reports utilizing such low catalyst loading.     

Four component reaction of aldehydes,isocyanides, Me3SiN3, and aliphatic alcohols catalyzed by indium triflate

In the presence of catalytic amount of indium(III) Lewis acids, the four component reaction of aldehydes, isocyanides, trimethylsilyl azide and aliphatic alcohols smoothly proceeded to give alkoxylated 1H-tetrazole products in good yields. In particular, In(OTf)₃ and In(ONf)₃ showed notably high level of catalytic activity in this reaction.     

Optically active helical polyisocyanides bearing chiral phosphine pendants: Facile synthesis and application in enantioselective Rauhut-Currier reaction

Three novel enantiopure phenyl isocyanide monomers with BH3-protected phosphine functional group were designed and synthesized.Polymerization of these monomers using a alkyne-Pd(Ⅱ) complex as a catalyst led to the formation of respective helical polyisocyanides in high yields with controlled molecular weights (Mns) and narrow molecular weight distributions (Mw/Mns).Removing the protecting BH3 groups afforded helical poly(phenyl isocyanide)s bearing phosphine pendants.Thanks to the chiral induction of monomer,the isolated helical polyisocyanides showed high optical activity,as revealed by circular dichroism (CD) and absorption spectroscopies and polarimetry.The helical structures of these polymers were quite stable in various organic solvents with different polarities and in a wide temperature range.Moreover,these helical polymers could be used as organocatalysts and showed good performance in enantioselective cross Rauhut-Currier reaction.The enantiomeric excess (ee) values of the isolated products of cross Rauhut-Currier reaction could be up to 90％.The polymer organocatalysts could be easily recovered from the reaction mixtures and reused at least five times in the reaction without significant loss of their enantioselectivities and catalytic activities.     

Efficient allylation of aldehydes promoted by carboxylic acids

A variety of carboxylic acids have been screened for mediating the allylation of aldehydes with allytributyltin in different solvents. A novel, general, and practical method of allylation of aldehydes promoted by carboxylic acids under mild reaction conditions has been developed. Among them, p-nitrobenzoic acid afforded high to quantitative yields of the homoallylic alcohol products, and can be easily recovered after workup by aqueous HCl. Glyoxylic acid self-catalyzed the allylation without adding any other promoter or catalyst to give the corresponding allylation product in good yield. The regioselectivity of the crotylation of aldehydes is tunable by controlling the acidity of the carboxylic acids. The crotylation of aldehydes produced the alpha-adduct as major products in moderate to good yields with CF(3)CO(2)H as a promoter. A possible mechanism for the allylation is also discussed.     

Silver-Catalyzed Three-Component 1,1-Aminoacylation of Homopropargylamines: α-Additions for Both Terminal Alkynes and Isocyanides

The reaction of secondary homopropargylamines, isocyanides, and water in the presence of a catalytic amount of silver acetate and subsequent purification by chromatography on silica gel afforded substituted proline amides in good to excellent yields. Primary homopropargylamines underwent a cyclizative Ugi–Joullié three-component reaction with isocyanides and carboxylic acids to afford functionalized N-acyl proline amides. High diastereoselectivity was observed in the synthesis of 4-alkoxy and 4,5-disubstituted proline derivatives. This work represents the first examples of a three-component cyclizative 1,1-aminoacylation of terminal alkynes.     

Highly efficient synthesis of 2,3-dihydroquinazolin-4(1H)-ones catalyzed by heteropoly acids in water

<正>Heteropoly acids efficiently catalyzed the cyclocondensation reaction of anthranilamide with aldehydes in water at ambient temperature and afforded the corresponding 2,3-dihydro-4(1H)-quinazolinones compounds in good to excellent yields.This method provides mild reaction conditions and clean reaction profiles,using a small quantity of catalyst and a simple workup procedure.     

Silver‐Catalyzed Three‐Component 1,1‐Aminoacylation of Homopropargylamines: α‐Additions for Both Terminal Alkynes and Isocyanides

The reaction of secondary homopropargylamines, isocyanides, and water in the presence of a catalytic amount of silver acetate and subsequent purification by chromatography on silica gel afforded substituted proline amides in good to excellent yields. Primary homopropargylamines underwent a cyclizative Ugi–Joullié three‐component reaction with isocyanides and carboxylic acids to afford functionalized N‐acyl proline amides. High diastereoselectivity was observed in the synthesis of 4‐alkoxy and 4,5‐disubstituted proline derivatives. This work represents the first examples of a three‐component cyclizative 1,1‐aminoacylation of terminal alkynes.     

A metal-free three components procedure for the synthesis of perfluoroalkyl substituted amidines

An interesting multicomponent reaction for the synthesis of perfluoroalkyl substituted amidines has been developed. By using perfluoroalkyl iodides, tert-butyl isocyanides and amines as the substrates, the reactions proceed via somophilic isocyanide insertion. In this catalytic system, no transition-metal catalyst, additional ligands and additives were required. The reaction proceed smoothly and a variety of desired amidines were obtained in moderate to excellent yields.     

Synthesis of 1-substituted tetrazoles via the acid-catalyzed [3+2] cycloaddition between isocyanides and trimethylsilyl azide

1-Substituted tetrazoles were synthesized via the [3+2] cycloaddition between isocyanides and trimethylsilyl azide in the presence of an acid catalyst and MeOH. Various 1-substituted tetrazoles were obtained in good to high yields. The reaction probably proceeds through the in situ formation of hydrazoic acid, followed by a successive [3+2] cycloaddition with the isocyanide activated by an acid.     

A ligand-free Pd-catalyzed cascade reaction: an access to the highly diverse isoquinolin-1(2H)-one derivatives via isocyanide and Ugi-MCR synthesized amide precursors

A novel ligand-free palladium-catalyzed cascade reaction for the synthesis of highly diverse isoquinolin-1(2H)-one derivatives from isocyanide and amide precursors synthesized by Ugi-MCR has been developed. A broad variety of acids, amines, and isocyanides were used as starting materials for Ugi-MCR leading to various amide precursors, which in turn provided entry into diverse isoquinolin-1(2H)-one derivatives. The reaction proceeds through tandem isocyanide insertion with intramolecular cyclization followed by a Mazurciewitcz-Ganesan type sequence to provide isoquinoline-1(2H)-one derivatives in moderate to good yields.     

Synthesis of Sulfamate‐Fused 2‐Aminopyrroles via an Isocyanide‐Based Three Component [1+2+2] Annulation

An efficient preparation of sulfamate‐fused 2‐aminopyrroles was achieved through an isocyanide‐based three‐component [1+2+2] annulation of isocyanides, dialkyl acetylenedicarboxylates, and sulfamate‐derived cyclic imines in good to excellent yields (up to 99 %). This reaction proceeds smoothly without any activation or modification of substances under neutral and metal‐free conditions. The reaction could also be conveniently performed on a gram scale.     

Isocyanide based multicomponent reactions of oxazolidines and related systems

N-Alkyloxazolidines react in a multicomponent reaction with carboxylic acids and isocyanides to give N-acyloxyethylamino acid amides. The previously reported reaction conditions were improved using a design of experiments approach (DoE). Under the optimised conditions, good yields of the N-acyloxyethylamino acid amide products are obtained both via a three- or four-component approach from N-alkylethanolamines, aldehydes/ketones, isocyanides and carboxylic acids. The reaction of oxazolidines without a nitrogen substituent was found to give either the expected Ugi products or the N-acyloxyethylamino acid amides depending on the choice of reaction conditions. Optimised reaction conditions were also developed for the ring-expansion of oxazolidines to morpholin-2-ones via reaction with an isocyanide followed by hydrolysis. The mechanistic pathway of the multicomponent reaction was briefly investigated using an ¹⁸O labelling experiment. The carboxylic acid component can be replaced by a range of other acidic nucleophiles including thiobenzoic acid, thiophenol or 5-phenyltetrazole, which are incorporated via an alternative pathway. These latter reactions can also be applied to 2-aminotetrahydrofurans, 2-aminotetrahydropyrans or 4-hydroxybut-2-one, further extending the structural diversity of the multicomponent reaction products.     

An efficient chemoselective synthesis of O-vinylaryl systems using acetylenic esters and dihydroxybenzenes in the presence of triphenylphosphine or alkyl isocyanides

<正>The addition of 2,4-dihydroxyaceto(and benzo)phenone to propiolic ester is catalyzed by triphenylphosphine or tert-butyl isocyanide to form O-vinyl aryl derivatives in fairly good yields.