Ring‐Opening of Benzocyclobutenol with Mild Bases and Trapping with Dieneophiles

The treatment of benzocyclobutenol with a mild base has been investigated. This reaction results in an electrocyclic opening of the cyclobutene to the corresponding o‐quinodimethane, which has been successfully treated with aldehydes and electron‐deficient alkenes to form benzolactols and benzocyclohexenes respectively.     

Convenient ‘one-pot’ synthesis of 3,4-substituted tetrahydrothiophenes through tandem Michael-Henry and Michael-Michael reactions

In situ generated nitro alkenes underwent tandem Michael-Henry and Michael-Michael sequences leading to the ‘one-pot’ formation of 3,4-substituted tetrahydrothiophenes using the commercially available 1,4-dithiane-2,5-diol (the dimer of mercaptoacetaldehyde) or its 4-mercapto-2-butenoates derivatives as suitable bifunctional partners, respectively.     

Catalytic Isofunctional Reactions—Expanding the Repertoire of Shuttle and Metathesis Reactions

Transfer hydrogenation, alkene metathesis, and alkyne metathesis possess great value to the synthetic chemistry community. One of the key features of these processes is their reversibility, which can be attributed to the presence of the same number and type of functional groups in both the reactants and products, making these reactions isofunctional. These classic reactions have recently inspired the development of novel shuttle and metathesis reactions that offer great promise for synthetic chemistry. This Review describes and systematically categorizes both recent and older examples of shuttle and metathesis reactions other than transfer hydrogenation and alkene/alkyne metathesis.     

Radical and Radical–Ionic Multicomponent Processes

All in one pot! Radical, radical–ionic, and radical–organometallic MCR are highly convergent processes, representing a useful pathway to molecular and structural diversity (see scheme). This concept article highlights recent developments in the field and shows the potential of the strategy for the economical elaboration of various kinds of organic substrates.

     

A new ‘one-pot’ synthesis of 2-substituted 3-nitro pyrrolidines through a multicomponent domino reaction

An efficient ‘one-pot’ synthesis of the title compounds based on a multicomponent domino reaction between imines and 3-nitro-1-propanol methanesulfonate has been developed.     

Synthesis of Highly Substituted Cyclobutane Fused‐Ring Systems from N‐Vinyl β‐Lactams through a One‐Pot Domino Process

In this contribution, aminocyclobutanes, as well as eight‐membered enamide rings, have been made from N‐vinyl β‐lactams. The eight‐membered products have been formed by a [3,3]‐sigmatropic rearrangement, whereas the aminocyclobutanes have been derived from a domino [3,3]‐rearrangement/6π‐electrocyclisation process. The aminocyclobutanes have been obtained in a highly diastereoselective fashion. The cyclobutane ring system tolerates fusion even if adjacent quaternary centres are present. Systems containing up to four fused rings are readily accessible. The reaction profile has been investigated by using Gaussian 03. This study suggests that two reaction pathways for aminocyclobutane formation are possible. In one pathway the [3,3]‐sigmatropic rearrangement is the rate‐limiting step and in the second pathway the electrocyclisation is rate limiting. Taken together, these reactions should facilitate the construction of fused heterocycles.     

Carboncarbon bond formation by radical addition-fragmentation reactions of O-tert-alkyl enols and O-cyclopropylcarbinyl enols

Terminal alkenes of the type H₂CC(OR¹)X, in which R¹ is a tertiary alkyl or a 1-cyclopropylethyl group and X=Ph, OSiMe₂Bu^t, OEt or H, undergo radical-chain reactions with organic halides R²Hal to give carbonyl compounds R²CH₂C(O)X.     

Carbopalladation Cascades Using Carbon–Carbon Triple Bonds: Recent Advances to Access Complex Scaffolds

Alkynes are one of the most versatile functional groups as synthetic handles. They allow for a direct access to partially or fully substituted alkenes through difunctionalization reactions. A prominently utilized transformation for these sequences is the carbopalladation of alkynes, which can be followed by various termination steps such as aromatizations, dearomatizations, cross‐coupling reactions, or pericyclic processes, amongst others. This Minireview provides an overview of the recent literature published in the field of carbopalladation chemistry, both with a focus on methodology as well as its application in the syntheses of complex molecular scaffolds, natural products, and functional molecules.     

Dehydrobromination and Debromination Reactions of Cyclic Dibromosulfones

The dehydrobromination and debromination reactions of some α, β-dibromosulfones in a five-membered ring with sodium phenylthiolate, pyridine, and sodium methoxide have been studied. In general, phenylthiolate induces debromination elimination reactions while pyridine and methoxide induce dehydrobromination reactions.     

Multicomponent coupling reactions for organic synthesis: chemoselective reactions with amide-aldehyde mixtures

The acid-catalyzed condensation chemistry of simple amides and aldehydes provides a highly prolific source of diverse reactants for irreversible follow-up reactions. Amide-aldehyde mixtures have been successfully employed in multicomponent syntheses of N-acyl alpha-amino acids (via palladium-catalyzed amidocarbonylation) and various cyclohexene, cyclohexadiene, and benzene derivatives (via the amide-aldehyde-dienophile (AAD) reaction).     

Kinetic Relationships between Reactions in the Gas Phase and in Solution

Some recent examples of reactions proceeding both in the gas phase and in solution have been investigated to determine their kinetics and mechanisms. The ratio of the corresponding rate constants, k_G and k_L, of the elementary processes studied has been found to be about unity for unimolecular reactions and between 1 and 10 for bimolecular reactions. The mechanisms, overall rates, rate constants, and activation energies have been determined for the homogeneous gas reaction NOCl + Cl₂O = NO₂Cl + Cl₂ and the reaction NOCl + N₂O₅ = NO₂Cl + 2 NO₂, carried out in C₂F₃Cl₃.     

Regio‐, Peri‐, and Torquoselectivity in Hydroxy Heptatrienyl Cation Electrocyclizations: The Iso/Homo‐Nazarov Reaction

Competition : The electrocyclizations of 1‐ and 3‐hydroxyheptatrienyl cations (see scheme) have been computationally studied at the B3LYP/6‐311G(d) level. The 1‐hydroxy system clearly favors a 4e^? over a 6e^? process, while for the 3‐hydroxy isomer these mechanisms compete.

     

Photoinduced Multicomponent Reactions

The combination of multicomponent approaches with light‐driven processes opens up new scenarios in the area of synthetic organic chemistry, where the need for sustainable, atom‐ and energy‐efficient reactions is increasingly urgent. Photoinduced multicomponent reactions are still in their infancy, but significant developments in this area are expected in the near future.     

Enzyme promiscuity: first protein-catalyzed Morita-Baylis-Hillman reaction

The Morita-Baylis-Hillman reaction of cyclohexenone and p-nitro benzaldehyde is catalyzed by carrier proteins such as serum albumins or enzymes such as certain lipases, conversion of up to 35% and enantioselectivities of up to 19% being observed.     

Synthesis of new 2,5-dimethyl pyrrole derivatives from acetonylacetone

<正>Acetonylacetone 1 was treated with thiourea,aniline,glycine and glutamic acid to give pyrrole derivatives 2,3,5,and 9 by Paal-Knorr reaction,respectively.Then 3 was successfully transformed into the related pyrrole derivative 4 by Mannich reaction. Compounds 6,7 and 8 were obtained by reacting 5 with phenethyl alcohol,phenylallylic alcohol and leaf alcohol by esterification reactions,respectively.The structures of all new products were elucidated by IR,NMR and HRMS spectra.