Synthesis of Spiro[piperidine‐3,3′‐oxindoles] via Gold(I)‐Catalyzed Dearomatization of N‐Propargyl‐ and N‐Homoallenyl‐2‐bromotryptamines

N‐Propargyl‐ and N‐homoallenyl‐2‐bromo‐β‐tryptamines undergo gold(I)‐catalyzed dearomatizing cyclizations to afford 2‐bromospiroindolenines that are in situ hydrolyzed to furnish spirooxindoles in a one‐pot process. Tryptophane derivatives (R²=CO₂Et) led upon cyclization to chiral spirooxindoles in excellent diastereoselectivities.

     

Palladium Nanoparticles in Water: A Reusable Catalytic System for the Cycloetherification or Benzannulation of α‐Allenols

A convenient ligand‐free catalytic system has been developed for the chemoselective cyclization reaction of various α‐allenol derivatives by palladium nanoparticles (PdNPs) in an aqueous reaction medium.

     

Iodothiocyanation/Nitration of Allenes with Potassium Thiocyanate/Silver Nitrite and Iodine

Direct strategies for the iodothiocyanation and iodonitration of allenes have been developed. In this process, potassium thiocyanate/silver nitrite and molecular iodine are used as the source of SCN, ONO₂ and iodine to provide the desired products in moderate to good yields with high stereoselectivity.

     

Scope and Limitations of Palladium‐Catalyzed Cross‐Coupling Reactions with Organogold Compounds

Five different alkenylgold(I) phosphane complexes were prepared and then investigated in [1,1′‐bis(diphenylphosphino)ferrocene]palladium(II) dichloride‐catalyzed cross‐coupling reactions with different aryl halides, heterocyclic halides, an alkenyl halide, an alkynyl halide, allylic substrates, benzyl bromide and an acid chloride. With regard to the halides, the iodides were highly reactive, bromides or chlorides gave significantly reduced yields or failed, allylic acetates failed, too. The cross‐coupling partners contained a number of different functional groups, while free carboxylic acids did not deliver cross‐coupling products and o,o‐disubstituted arenes failed as well, a broad range of other functional groups like nitro groups, nitrile groups, ester groups, α,β‐unsaturated ester groups and lactones, aldehydes, alkoxy groups, pyridyl groups, thienyl groups, unprotected phenols and anilines, even aryl azides were tolerated. The structures of one alkenylgold(I) species and of four of the cross‐coupling products were proved by crystal structure analyses.     

Development of a New Spiro‐BOX Ligand and Its Application in Highly Enantioselective Palladium‐Catalyzed Cyclization of 2‐Iodoanilines with Allenes

In this communication, we report the synthesis of a new chiral spiro‐bisoxazoline ligand, i.e., β‐naphthylmethyl‐substituted spiro‐BOX [(R_a,S,S)‐ L7 ] and have successfully applied it to the palladium‐catalyzed enantioselective cyclization reaction of simple allenes with o‐aminoiodobenzenes, affording highly optically active 3‐alkylideneindolines in good yields with excellent enantiomeric excesses.     

Stereocontrolled synthesis of the taxol C‐13 side chain: Methyl (2R,3S)‐3‐benzoylamino‐2‐hydroxy‐3‐phenylpropanoate

Addition of lithiated methoxyallene 5 to literature‐known amino aldehyde 3 followed by ozonolysis provided syn‐configurated α‐hydroxy‐β‐amino ester 6 in moderate overall yield and with an ee of 90%. The predominant formation of syn‐compounds may be due to a chelate controlled addition step.     

Palladium‐Catalyzed Highly Chemo‐, Regio‐ and Stereoselective Synthesis of Eight‐ to Ten‐Membered Lactones from Allenyl 3‐Oxoalkanoates and Organic Halides

A highly chemo‐, regio‐, and stereoselective synthesis of eight‐ to ten‐membered lactones via the coupling cyclization of readily available allenyl 3‐oxoalkanoates and organic halides through an anti‐π‐allylic palladium intermediate is reported. The yields ranged from moderate to good.     

Allene as an alternative functional group for drug design: effect of C--C multiple bonds conjugated with quinazolines on the inhibition of EGFR tyrosine kinase

A series of allenic quinazolines were synthesized as receptor tyrosine kinase inhibitors by using a simple protocol for palladium-catalyzed allene transformation. Among the compounds synthesized, two allenic 4-anilinoquinazolines selectively suppressed epidermal growth factor receptor (EGFR) tyrosine kinase activity in vitro. According to immunoblot analysis, the allenic quinazolines inhibited the EGF-mediated phosphorylation of EGFR and its downstream kinases in A431 cells. Furthermore, one of these allenic quinazolines decreased the proliferation of A431 cells through the induction of cell-cycle arrest and apoptosis.     

Highly Regio‐ and Stereoselective Iodohydroxylation of Non‐ Heteroatom‐Substituted Allenes: An Efficient Synthesis of 4‐[3′‐Hydroxy‐2′‐iodoalk‐1′(Z)‐enyl]‐2(5H)‐furanone Derivatives

An efficient protocol for the highly regio‐ and stereoselective synthesis of 4‐(3′‐hydroxy‐2′‐iodoalk‐1′(Z)‐enyl)furan‐2(5H)‐one derivatives via selective iodohydroxylation of non‐heteroatom‐substituted allenes, i.e., 4‐allenyl‐2(5H)furanones, has been developed. The regio‐ and stereoselectivity of this reaction may be controlled by the electronic and steric effects of the furanone ring.     

The rearrangement of fatty cyclopropenoids in the presence of boron trifluoride

The destruction of the cyclopropenoid ring system of methyl 9,10 methyleneoctadec-9-enoate (methyl sterculate) with boron trifluoride etherate has been shown to give a complex mixture of products, including methyl esters of C₁₉ allenes (12%), a C₁₈ alkyne (11%) and a variety of C₁₉ and C₂₀ conjugated dienes containing either a methyl or methylene branch. The methylene group lost from the methyl sterculate reactant in the formation of methyl octadec-9-ynoate is incorporated into a second molecule of reactant to yield a mixture of methyl 9-methylene-trans-nonadec-10-enoate and the 11-methylene-trans-9-isomer.