Rapid construction of five contiguous stereocenters in a multi-cascade reaction

A palladium-catalyzed cascade approach for the synthesis of 3,3a,4,6,7,8,9,9a-octahydro-1H-benzo[f]isoindole-1,5(2H)-diones

A synthetic method for the preparation of 3,3a,4,6,7,8,9,9a-octahydro-1 H-benzo[ f]isoindole-1,5(2 H)-diones from 1,6-dienes and vinyl iodides is developed using PdCl2(PPh3)2 as the catalyst. The presented approach exhibits a good functional group tolerance and affords moderate yields of the products. A mechanism is also proposed.

Direct Access to Fused Salicylaldehydes and Salicylketones from Tetraynes

A facile method for the synthesis of fused, multifunctionalized salicylaldehydes and salicylketones by a one-pot, three-step cascade hexadehydro-Diels-Alder (HDDA) reaction of tetraynes followed by an intermolecular aldehyde/ketone reaction and hydroxylation is reported. Target compounds were prepared by the condensation of malonates with 3-bromo-1-propyne, and the resulting 2,2-di(1-propyn-3-yl)malonates underwent cross-coupling with phenylethynyl bromides to afford 2,2-di(5-phenyl-2,4-pentadiynyl)malonates, which underwent intramolecular cyclization to produce bicyclic salicylaldehydes. The overall transformation involves the formation of four new C-C bonds and one new C_aryl -O bond through both intramolecular and intermolecular reactions. The reaction is easy to perform, proceeds under mild conditions, and exhibits excellent regioselectivity. Water, a simple and readily available reagent, was employed as the OH source. A plausible reaction mechanism is proposed for this new annulation based on isotopic substitution experiments.

One-step synthesis of diazaspiro[4.5]decane scaffolds with exocyclic double bonds

Unactivated yne-en-ynes reacted with a range of substituted aryl halides in the presence of Pd(OAc)2-PPh3 to afford diazaspiro[4.5]decane with exocyclic double bonds. Three carbon-carbon bonds are formed in this domino reaction, which involves highly regioselective C-C coupling and spiro scaffold steps.

Convenient one-step construction of yne-functionalized aryl halides through domino cyclization from tetraynes

An efficient method for the construction of fused yne-substituted aryl halides by reaction of unactivated linear tetraynes with allyl halides via domino C-C coupling and formation of C-X bonds in the presence of Pd(OAc)2/PPh3 was developed.

4-(6-Benzyl-7-oxo-1,2,3,4,5,5a,5a1,6,7,7a,8,12b-dodecahydrobenzo[f]cycloocta[cd]isoindol-8-yl)benzonitrile

In the title compound, C₃₁H₃₀N₂O, the cis-fused cyclo­hexene and cyclo­octane rings adopt boat and boat-chair conformations, respectively. The essentially planar five-membered N-heterocyclic ring [r.m.s. deviation = 0.017 (1) Å] is cis- and trans-fused, respectively, with the cyclo­hexene and cyclo­octane rings. In the crystal, mol­ecules are linked into inversion dimers through pairs of weak C—H⋯O inter­actions.

(E)-4-[(1-Benzyl-4-benzyl-idene-2,5-di-oxopyrrolidin-3-yl)meth-yl]benzalde-hyde 0.25-hydrate

The crystal structure of the title compound, C₂₆H₂₁NO₃·0.25H₂O, reveals one stereogenic centre in the mol­ecule. Nevertheless, due to the observed centrosymmetric space group, both enanti­omers are present in the crystal packing. The water molecule of crystallisation is located on a crystallographic inversion center. The mol­ecule contains one five-membered ring (A) and three six-membered rings (benzyl ring B, benzyl­idene ring C and formyl­benzyl ring D). All four rings are not coplanar: the dihedral angles between rings A and B, A and C, and A and D are 70.35 (9), 33.8 (1) and 60.30 (9)°, respectively. In the crystal, pairs of weak C—H⋯O inter­actions lead to the formation of centrosymmetric dimers. Additional C—H⋯O inter­actions link the dimers into chains along [011].

Ethyl 4-acetyl-5-oxo-3-phenyl-hexa-noate

The reaction of ethyl 3-bromo-3-phenyl­propano­ate with pentane-2,4-dione, in the presence of palladium(II) acetate and triphenyl­phosphine, in dimethyl­formamide, unexpectedly gave the title product, C₁₆H₂₀O₄. The mol­ecule contains one chiral C atom but the crystal is racemic. In the crystal, neighboring mol­ecules form a chain along [100] through three weak C—H⋯O inter­actions. Furthermore, a double-stranded structure is formed through weak C—H⋯O inter­actions between two parallel chains.

Synthesis of polycyclic nitrogen heterocycles via alkene aminopalladation/carbopalladation cascade reactions

A new method for the synthesis of tricyclic nitrogen heterocycles from N,2-diallylaniline derivatives is described. These transformations proceed via sequential alkene aminopalladation of an intermediate L(n)Pd(Ar)(NRR') species followed by alkene carbopalladation of the resulting L(n)Pd(Ar)(R) complex. Both alkene insertion steps occur in preference to C-N or C-C bond-forming reductive elimination. An unusual 1,3-palladium shift occurs when 2-Allyl-N-(2-vinylphenyl)aniline is employed as substrate, which yields a tetracyclic molecule with three contiguous stereocenters.