Formal Cycloaddition Reactions Research Articles

The reactions of diazo compounds with lactones. Part 2.† The reaction of cyclic 2-diazo-1,3-dicarbonyl compounds with diketene: benzofuran formation

Cyclic 2-diazo-1,3-dicarbonyl compounds react with diketene in the presence of rhodium(II) salts to give benzofurans as the major isolated products. The formation of intermediate products with exocyclic double bonds which isomerise to benzofurans provides support for the proposed mechanism which involves initial formation of a dioxaspirooctenone by a formal dipolar cycloaddition reaction of a carbenoid to the exocyclic double bond of diketene followed by the loss of carbon dioxide. Acyclic 2-diazo-1,3-dicarbonyl compounds give furans in poor yield.

ChemInform Abstract: Formal Cycloaddition Reactions of Vinylogous Amides with α,β‐Unsaturated Iminiums. A Strategy for Constructing Piperidinyl Heterocycles.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Formal Cycloaddition Reactions of Vinylogous Amides with α,β-Unsaturated Iminiums. A Strategy for Constructing Piperidinyl Heterocycles

A formal [3 + 3] cycloaddition strategy for constructing piperidinyl heterocycles from vinylogous amides and α,β-unsaturated iminiums is described here. These reactions proceed well, leading to various heterocycles that could serve as useful synthetic building blocks. Comparative studies between the reactivities of vinylogous amides and other 1,3-diketo systems have also been examined. Preferences for the nitrogen atom during the electrocyclic ring closure step are noted in these reactions, and preliminary calculations suggest that these preferences could result from electronic factors.

Cycloadditions of allylsilances. Part 10. Stereoselective Construction of Ring Systems by Cycloaddition Reactions of allyltriisopropylsilance

Allyltriisopropylsilane is a useful reagent for the stereoselective construction of various ring systems by Lewis acid promoted formal cycloaddition reactions. The reaction of allyltriisopropylsilane as a synthetic equivalent of a 1,3-dipole in [3+2] and [3+3] cycloadditions provides cyclopentanes, tetrahydrofurans, and tetrahydronaphthalenes. [2+2] and [2+3] Cycloadditions of allyltriisopropylsilane as a synthetic equivalent of a 1,2-dipole provide cyclobutanes, oxetanes, azetidines, and dihydrofurans.

ChemInform Abstract: ZnCl2 Promoted Formal (3 + 2) Cycloaddition Reactions of 2‐Alkoxy‐1,4‐ benzoquinones with 2H‐Chromenes.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ZnCl2Promoted Formal (3+2) Cycloaddition Reactions of 2-Alkoxy-1,4-benzoquinones with 2H-Chromenes

Abstract A simple, mild, inexpensive and highly efficient method for the synthesis of 2,2-dimethyldihydropyranopterocarpans (4a–h and 5a–b) by formal (3+2) cycloaddition reactions of 2-alkoxy-1,4-benzoquinones (3a–b) with 2H-chromenes (1a–d and 2) using ZnCl2 at room temperature has been developed.

ChemInform Abstract: Regioselective Synthesis of Substituted Pterocarpans and Pterocarpenes. Lewis Acid Ti(IV) Promoted Formal (3 + 2) Cycloaddition Reactions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Regioselective synthesis of substituted pterocarpans and pterocarpenes. Lewis acid Ti (IV) promoted formal (3+2) cycloaddition reactions.

A synthesis of novel pterocarpans ( 8a–e, 10a–c and 11a–e) and pterocarpenes ( 7a–d and 9a–c) has been carried out. This method involves the Lewis acid Ti (IV) promoted formal (3+2) cycloaddition reaction of 2-alkoxy-1,4-benzoquinones ( 6a–c) with appropriately substituted 2 H-chromenes ( 1a–b, 2a–b and 5) at −78°C.

ChemInform Abstract: Formal (3 + 2) Cycloaddition Reactions of 1‐Methyl‐2‐(methylthio( trimethylsilylmethylimino)methylimino)‐1,2‐dihydropyridine and Related Compound with Carbonyl Compounds Promoted by Fluoride Ion.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Formal (3+2) Cycloaddition Reactions of 1-Methyl-2-(methylthio-(trimethylsilylmethylimino)methylimino)-1,2-dihydropyridine and Related Compound with Carbonyl Compounds Promoted by Fluoride Ion.

Reaction of 1-methyl-2-[methylthio(trimethylsilylmethylimino)methylimino]-1, 2-dihydropyridine (1), prepared from 2-amino-1-methyl-pyridinium iodide in 3 steps, with carbonyl compounds in the presence of 2 eq of cesium fluoride in acetonitrile afforded 2-(1-methyl-1, 2-dihydropyridylidene)aminooxazoline derivatives (12), which correspond to formal [3+2] cycloadducts of the aminonitrile ylid. Further, compound 1 reacted with carbonyl compounds in the presence of a catalytic amount of tetra-n-butylammonium fluoride (TBAF) to give corresponding cycloadducts.

Cyclopropenes electrophiles : Reactions du morpholino-1 cyclohexene avec quelques esters GEM- DI methylcyclopropeniques; Acces a des analogues halopyrethriques (1).

Electrophilic cyclopropene esters react with 1-morpholino cyclohexene to give various products depending on the second substituent of the cyclopropene double bond. Enamine alkylation is observed -but not always- as well as different formal cycloaddition reactions.

Reactions de cyclopropenes electrophiles avec les Enamines et ynamines. Cycloadduits bicyclopentaniques et analogues halochrysanthemiques

Electrophilic cyclopropene esters mainly undergo formal cycloaddition reactions with ynamines and enamines. While the former reagents lead solely of cyclopentadiene enaminoesters, with the latter different products are formed, which can all be derived from a common zwitterionic intermediate. Enamines react in part with conservation of the cyclopropane ring, in contrast to their reactions with cyclopropenones and triafulvenes, thus allowing the synthesis of cyclopropene derivatives as illustrated here with halopyrethroids.