Recent advances in the chemistry of 2-(2-oxoalkylidene)tetrahydrofurans

Domino reactions of chromones with activated carbonyl compounds

Domino reactions of chromones with activated carbonyl compounds, such as dimethyl acetone-1,3-dicarboxylate and 1,3-diphenylacetone, and with 1,3-bis(silyloxy)-1,3-butadienes, electroneutral equivalents of 1,3-dicarbonyl dianions, allow for a convenient synthesis of a great variety of products. The regioselectivity and course of the reaction depends of the substituent located at carbon C3 of the chromone moiety and also on the type of nucleophile employed.

Small and Smart: Adventures in Epihalohydrin Chemistry

The present personalized account aims to highlight reactions of epichlorohydrin and epibromohydrin with free and masked dianions. These reactions permit convenient syntheses of a variety of products, such as 2-(alkylidene)tetrahydrofurans (which can be further functionalized by hydrogenation or ring-transformation reactions), cyclopropanes, γ-butyrolactams, oxazines, oxazolo[3,4-b]pyridazin-7-ones, or 2-(alkylidene)thiazolidines. In general, the reactions proceed with very good regioselectivity.

1 Introduction

2 Reactions of Masked Dianions

2.1 Synthesis of 2-(Alkylidene)tetrahydrofurans

2.2 Functionalization of 2-(Alkylidene)tetrahydrofurans

3 Reactions of Free Dianions

3.1 Synthesis of 2-(Alkylidene)tetrahydrofurans

3.2 Functionalization of 2-(Alkylidene)tetrahydrofurans

3.3 Synthesis of γ-Butyrolactams

3.4 Synthesis of 5,6-Dihydro-4H-1,2-oxazines

3.5 Synthesis of Oxazolo[3,4-b]pyridazin-7-ones

3.6 Synthesis of Cyclopropanes

3.7 Synthesis of 2-(Alkylidene)thiazolidines

4 Conclusions

Adventures in 1,1-Diphenylacetone Dianion Chemistry

The present personalized account highlights reactions of the dianion of 1,1-diphenylacetone and its applications. From a study directed towards the regioselectivity of such reactions a new allene synthesis via allene dianions was found by serendipity. In addition, reactions of allene dianions with various electrophiles have been studied.

1 Introduction

2 Cyclizations of the Dianion of 1,1-Diphenylacetone

2.1 Reaction with Bis(cyclopentadienyl)zirconium Dichloride

2.1 Reactions with Dichlorosilanes

2.1 Reactions with Difluorosilanes

2.1 Reactions with Ketones and Dielectrophiles

3 Regioselectivity of Dianion Reactions

4 Allene Dianions from Silyl Enol Ethers

5 Scope of the Reactions of Allene Dianions

6 Reactions of Allene Dianions with Ketones

7 Reactions of Allene Dianions with Nitriles

8 Conclusions

α-Iodo-α,β-Unsaturated Ketones as Vicinal Dielectrophiles: Their Reactions with Dinucleophiles Provide New Annulation Protocols for the Formation of Carbo- and Heterocyclic Ring Systems

α-Iodo-α,β-unsaturated ketones such as compound 1 serve as vicinal dielectrophiles and react with a range of dinucleophiles including pentane-2,4-dione and 1,3-indandione to produce [3 + 2]- and [2 + 1]-adducts such as 5 and 38, respectively. [4 + 2]- and [5 + 2]-cycloadducts have been obtained from compound 1 by related means. Preliminary studies reveal that α-iodinated α,β-unsaturated esters can also participate in at least some of these same processes.

Three-component synthesis of α-indole-β-sulfonyl tetrahydrofurans under metal-free conditions

An efficient multi-component reaction has been developed for the synthesis of 2,3-disubstituted tetrahydrofurans in a “one pot” manner, starting from readily available 2-arylindoles, arylsulfonyl azides, and tetrahydrofuran under simple and easily operated reaction conditions.

Domino Reactions of Chromones with Heterocyclic Enamines

Domino reactions of heterocyclic enamines with chromone derivatives provides a convenient synthesis of a great variety of annulated heterocyclic ring systems. The course of the reaction depends on the type of substituent located at position 3 of the chromone. Reactions of 3-unsubstituted chromones, 3-nitrochromones, and 3-halochromones proceed by conjugate addition of the carbon atom of the enamine to carbon C-2 of the chromone, ring cleavage, and recyclization via the chromone carbonyl group. In the case of 3-formylchromes, 3-dichloroacetylchromone, 3-perfluoroalkanoylthiochromones, 3-(2-fluorobenzoyl)chromones, and 3-methoxalylchromones the final cyclization proceeds via the carbonyl group located outside the chromone moiety. The functional groups located at the carbonyl group at position 3 of the chromone allow for further synthetic transformations including additional ring closures.

Contents

1 Introduction

2 3-Unsubstituted Chromones

3 3-Nitrochromones

4 3-Formylchromes

5 3-Dichloroacetylchromone

6 3-Perfluoroalkanoylthiochromones

7 3-Methoxalylchromones

8 3-(2-Fluorobenzoyl)chromones

9 3-Halochromones

10 Chromone-3-carboxylic Acids

11 Conclusions

Synthesis and Reactions of 1,3,5-Tri- and 1,3,5,7-Tetracarbonyl Compounds

The reaction of 1,3-bis(silyloxy)-1,3-butadienes with functionalized and nonfunctionalized acid chlorides and bis(acid chlorides) gives rise to the formation of a great variety of 1,3,5-tri- and 1,3,5,7-tetracarbonyl compounds and cyclic products derived from them. Examples include functionalized and nonfunctionalized 3,5-dioxopentanoates, 3,5-dioxopimelates, 3-alkylidene-3H-isobenzofuran-1-ones, salicylates, 3(2H)furanones, and 3-oxo-4-sulfonylesters. Methylation and cyclopropanation reactions of 1,3,5-tri- and 1,3,5,7-tetracarbonyl compounds do not provide access to the expected permethylated and cyclopropanated polycarbonyl compounds. However, the latter could be prepared by stepwise protocols. The reaction of 1,3,5-tri- and 1,3,5,7-tetracarbonyl compounds with dinucleophiles resulted in cyclization reactions to give a variety of heterocyclic structures.

1 Introduction

2 Reactions of 1,3-Bis(silyloxy)-1,3-butadienes with Acid Chlorides

3 Reactions of 1,3,5-Tri- and 1,3,5,7-Tetracarbonyl Compounds

4 Conclusion

Site-selective Suzuki-Miyaura cross-coupling reactions of 2,3,4,5-tetrabromofuran

Suzuki-Miyaura reactions of 2,3,4,5-tetrabromofuran allow a convenient and site-selective synthesis of mono-, di- and tetraarylfurans which are not readily available by other methods.