Pd-catalyzed autotandem C-C/C-C bond-forming reactions with tosylhydrazones: synthesis of spirocycles with extended π-conjugation.

A new Pd-catalyzed autotandem process is presented by the reaction of tosylhydrazones of cyclic ketones and 2,2'-dibromobiphenyls and related systems. The process involves cross-coupling with tosylhydrazone followed by an intramolecular Heck reaction and gives rise to spirocyclic structures. Noteworthy, two C-CAr bonds are formed on the hydrazonic carbon during the process.

Gold(I)-catalyzed hydroarylation reaction of aryl (3-iodoprop-2-yn-1-yl) ethers: synthesis of 3-iodo-2H-chromene derivatives.

An efficient entry to the preparation of elusive 4-unsubstituted-3-iodo-2H-chromenes has been accomplished as result of a catalytic cyclization. Thus, upon exposition of [(3-iodoprop-2-yn-1-yl)oxy]arenes to IPrAuNTf2 (3 mol %), in 1,4-dioxane at 100 °C, the desired heterocyclic motif is readily assembled. This process nicely tolerates a variety of functional groups and, interestingly, it is compatible with the presence of strong electron-withdrawing groups attached to the arene.

Rhodium-catalyzed carbene transfer to alkynes via 2-furylcarbenes generated from enynones.

A rhodium-catalyzed carbene transfer to alkynes is reported. Easily available enynones served as the carbene source replacing diazocompounds. The overall process involved a cyclization-cyclopropenation-ring enlargement sequence.

Regioselective synthesis of oxepinones and azepinones by gold-catalyzed cycloisomerization of functionalyzed cyclopropyl alkynes.

A regioselective synthesis of oxepinones and azepinones in good to excellent yields from alkynylcyclopropanecarboxylic acid derivatives is described. This novel cycloisomerization cascade process consists of a nucleophilic addition followed by a cyclopropane ring-opening, where both donor and acceptor groups are required as substituents of the cyclopropane ring.

One-pot direct C-H arylation of arenes in water catalysed by RuCl3·nH2O-NaOAc in the presence of Zn.

The inexpensive and commercially available catalytic system RuCl3·nH2O-NaOAc-Zn is active in water for the direct C-H arylation of arenes with aryl/heteroaryl chlorides. The reaction can be accelerated by the use of microwave irradiation and can also be scaled up to a multi-gram scale with excellent isolated yields.

New Ag(I)-iminophosphorane coordination polymers as efficient catalysts precursors for the MW-assisted Meyer-Schuster rearrangement of propargylic alcohols in water.

Treatment of the N-thiophosphorylated iminophosphorane ligands (PTA)═NP(═S)(OR)2 [PTA = 1,3,5-triaza-7-phosphaadamantane, 3a and 3b] and (DAPTA)═NP(═S)(OR)2 [DAPTA = 3,7-diacetyl-1,3,7-triaza-5-bicyclo[3.3.1]nonane, 4a and 4b] with an equimolecular amount of AgSbF6 leads to high-yield formation of the new one-dimensional coordination polymers [Ag{μ(2)-N,S-(PTA)═NP(═S)(OR)2}]x[SbF6]x (5a and 5b) and [Ag{μ(2)-O,S-(DAPTA)═NP(═S)(OR)2}]x[SbF6]x (6a and 6b), respectively.

Catalytic generation and selective heterocoupling of two electron-rich alkenes.

Complex heterocyclic products were synthesized from simple alkynamine and alkynol derivatives in a double cycloisomerization/heterodimerization cascade reaction. The reaction includes the heterocoupling reaction of two different electron-rich alkenes and leads to the formation of four new bonds and three stereocenters (two of them quaternary).

Synthesis and reactivity of new rhenium(I) complexes containing iminophosphorane-phosphine ligands: application to the catalytic isomerization of propargylic alcohols in ionic liquids.

[ReBr(CO)5] reacts with the iminophosphorane-phosphine ligands Ph2PCH2P(═NR)Ph2 (R = P(═O)(OEt)2 (1a), P(═O)(OPh)2 (1b), P(═S)(OEt)2 (1c), P(═S)(OPh)2 (1d), 4-C6F4CHO (1e), 4-C6F4CN (1f), 4-C5F4N (1g)) affording the neutral complexes [ReBr(κ(2)-P,X-Ph2PCH2P{═NP(═X)(OR)2}Ph2)(CO)3] (X = O, R = Et (2a), Ph (2b); X = S, R = Et (2c), Ph (2d)) and [ReBr{κ(2)-P,N-Ph2PCH2P(═NR)Ph2}(CO)3] (R = P(═O)(OEt)2 (3a), P(═O)(OPh)2 (3b), 4-C6F4CHO (3e), 4-C6F4CN (3f), 4-C5F4N (3g)). The reactivity of the cationic complex [Re(κ(3)-P,N,S-Ph2PCH2P{═NP(═S)(OPh)2}Ph2)(CO)3][SbF6] (4d) has been explored allowing the synthesis of the cationic [Re(L)(κ(2)-P,S-Ph2PCH2P{═NP(═S)(OPh)2}Ph2)(CO)3][SbF6] (L = acetone (5a), CH3C≡N (5b), pyridine (5c), PPh3 (5d)) and the neutral [ReY(κ(2)-P,S-Ph2PCH2P{═NP(═S)(OPh)2}Ph2)(CO)3] (Y = Cl (6a), I (6b), N3 (6c)) complexes. The catalytic activity of complex 4d in the regioselective isomerization of terminal propargylic alcohols HC≡CCR(1)R(2)(OH) into α,β-unsaturated aldehydes R(1)R(2)C═CHCHO or ketones R(3)R(4)C═CR(1)COMe (if R(2) = CHR(3)R(4)) under neutral conditions in ionic liquids has being studied.

Gold-catalyzed synthesis of tetrahydrocarbazole derivatives through an intermolecular cycloaddition of vinyl indoles and N-allenamides.

A gold-catalyzed formal [4+2] cycloaddition of vinyl indoles and N-allenamides leading to tetrahydrocarbazoles is described. Moreover, new multicomponent reactions of vinyl indoles with two allene molecules are reported.

A catalytic multicomponent coupling reaction for the enantioselective synthesis of spiroacetals.

The first multicomponent catalytic asymmetric synthesis of spiroacetals has been described. Hybrid molecules comprising a spiroacetal scaffold (a natural-product inspired scaffold) and an α-amino acid motif (a privileged fragment) are easily available through a gold phosphate-catalysed one-pot three component coupling reaction of alkynols, anilines and glyoxylic acid.

Base- and metal-free C-H direct arylations of naphthalene and other unbiased arenes with diaryliodonium salts.

A novel metal-free direct arylation of unbiased arenes with diaryliodonium triflates in a process where the use of solvents and additives is not required has been established.

Copper(I)-catalyzed [3+1] cycloaddition of alkenyldiazoacetates and iminoiodinanes: easy access to substituted 2-azetines.

The copper(I)-catalyzed reaction of alkenyldiazoacetates and iminoiodinanes affords functionalized azetine derivatives. This process is consistent with the formation of an aziridinyldiazoacetate intermediate, which gives rise to the four-membered heterocycles by metal-catalyzed ring expansion. The resulting azetine structure is a direct precursor of azeditine-2-carboxylic acid derivatives (EWG = electron-withdrawing group).

Synthesis of polysubstituted isoquinolines through cross-coupling reactions with α-alkoxytosylhydrazones.

A Pd-catalyzed cross-coupling reaction of α-alkoxytosylhydrazones with sulfonates derived from salicyl aldehydes gives rise to protected 1,5-dicarbonyl compounds. Treatment with ammonium hydroxide readily transforms these alkenes into isoquinolines with diverse substitution patterns at positions 3 and 4. In a similar way, the employment of o-cyanononaflates in the coupling reaction, followed by treatment with an organometallic, provides isoquinolines that incorporate substitution also at position 1.

Enantioselective multicomponent synthesis of fused 6-5 bicyclic 2-butenolides by a cascade heterobicyclisation process.

The successive coupling of an alkoxy(aryl/heteroaryl)carbene complex of chromium with either a ketone or an imide lithium enolate and then a 3-substituted (H, TMS, PhCH(2), PhCH(2)CH(2), Me) propargylic organomagnesium reagent has afforded novel hydroxy-substituted bicyclic [4.3.0]-γ-alkylidene-2-butenolides with three modular points that has allowed the efficient introduction of molecular complexity, including a homopropargylic alcohol core.

Scalable total synthesis of (-)-berkelic acid by using a protecting-group-free strategy.

Supply chain: the polycyclic core of (-)-berkelic acid (1) was constructed in just one step from very simple starting materials. The total synthesis of 1 involves a seven-step linear sequence. Protection/deprotection steps were avoided and all but the last step were performed on a gram scale.