A new synthesis of dl-muscopyridine based on the regioselective cyclopentenone annulation

Sulphuric acid catalyzed ring closure of propargyl alcohol dianion adduct of 2-cyclododecenone gives bicyclo[10.3.0]pentadec-1(12),2-dien-13-one. 1,6-Conjugate addition of methyl group followed by ring-expansion and aromatization affords the title compounds.     

A new regiospecific synthesis of aryl ketones from palladocycles

Aromatic palladocycles undergo facile reaction with acid halides to reglospecifically provide aryl ketones In high yield.     

Palladium(II) acetate mediated oxidative cyclization of omega-unsaturated alpha-cyano ketones. A facile methylenecyclopentane annulation process

A highly efficient methylenecyclopentane annulation process has been developed based on the Pd(II)-mediated oxidative cyclization of omega-unsaturated alpha-cyano ketones, readily accessed via the Michael addition of 3-butenylmagnesium bromide with 2-cyano-2-cycloalkenones.     

A new stereoselective synthesis of (±)nootkatone by means of cyclopentenone annulation

The title sesquiterpene is synthesized by means of the new cyclopentenone annulation which involves acid-treatment of IIIb. The ester group of the resulting V is transformed selectively into isopropenyl appendage of the trans configuration to the two methyl groups. Successive ring-enlargement via a dibromomethyllithium adduct X has yielded (±)nootkatone.     

Ionic liquid-promoted regiospecific Friedlander annulation: novel synthesis of quinolines and fused polycyclic quinolines

Several room-temperature ionic liquids (ILs) based on 1-butylimidazolium salts with varying anions were synthesized and evaluated for the preparation of biologically active substituted quinolines and fused polycyclic quinolines using the Friedlander heteroannulation reaction. On screening, 1-butylimidazolium tetrafluoroborate [Hbim]BF4 was found to be the best ionic liquid for the heteroannulation reaction, and the reasons to this effect are well explained. The reactions proceed very well under relatively mild conditions without any added catalyst. The IL acts as a promoter for this regiospecific synthesis and can be recycled. By this green approach, various quinolines were prepared in excellent yields and purity and well-characterized.     

Intramolecular sulfur-ylide additions to ketones. A cyclopentane annulation1

Various 2-(3′-phenylthiopropyl)cycloalkanones were prepared from the corresponding cyclic ketones and subjected to S-alkylation by triethyloxonium tetrafluoroborate followed by potassium $\text{tert}$-butoxide treatment to give bicyclic epoxides with new five-membered carbocycles. A related cyclization to a six-membered ring was also observed.     

N-heterocyclic carbenes mediated cyano-phosphorylation of ketones

Cyanation-O-protection reaction of ketones with different cyanide sources catalyzed by N-heterocyclic carbenes is reported. Under the catalysis of 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, various ketones coupled with diethyl cyanophosphonate to produce cyanohydrin-O-phosphates with a quaternary carbon center in moderate to excellent yield. Furthermore, the reaction can be scaled-up easily and high yield maintained.     

Catalytic enantiospecific [3+2] annulation of aminocyclopropanes with ketones

An almost familiar ring: The first enantiospecific [3+2] annulation of donor-acceptor aminocyclopropanes with ketones is reported (see scheme; Phth=phthaloyl). The reaction is catalysed by tin(IV) chloride (5?mol?%) at -78?°C and gives aminotetrahydrofurans bearing a quaternary C5 atom in high yield, diastereoselectivity and enantiospecificity (see scheme).     

Aryl annulation of cyclic ketones via a magnesium carbometalation-6-pi- electrocyclization protocol

A new strategy for the aryl annulation of cyclic ketones is described. Palladium(0) coupling of a propargyl alcohol with the enol triflate of a ketone and addition of vinylmagnesium chloride generates a triene as a magnesium chelate that may be quenched with an electrophile. In some cases, the triene cyclizes under the reaction conditions. Aromatization is accomplished by exposure to manganese dioxide or dichlorodicyanoquinone (DDQ). [reaction: see text]     

A general preparation of pyridines and pyridones via the annulation of ketones and esters

A general preparation of pyridines 4a-f from stabilized ketones 3a-c and aryl ketones 3d-f is described. The annulation of stabilized esters 3g,h gives access to the corresponding 2-pyridones 4g,h. The annulation reactions proceed in fair to excellent yields (46-87%) with vinamidinium hexafluorophosphate salts 2a-d containing electron-withdrawing groups at the beta-position. The mechanism of the reaction was investigated by NMR and proceeds through the formation of a dienaminone intermediate.     

Strategy for cyclopentenone annulation of olefins: A general protocol for bicyclo [n.3.0] enone synthesis

Several bicyclic α-chloro enones obtained through Greene annulation of cyclic olefins are shown to undergo efficient, two step, enone transposition $\text{via}$ Luche reduction and aq. formic acid treatment. Application of this methodology to the formal synthesis of exaltone^® and (±)-muscone is described.     

Double-Mannich annulation of cyclic ketones using N,N-Bis(ethoxymethyl)alkylamine reagents

[Structure: see text] N,N-Bis(ethoxymethyl)alkylamines function as effective reagents in the double-Mannich annulation of cyclic ketone substrates, providing efficient access to a series of azabicyclic ketones. These ring systems are a useful scaffold for the four-step synthesis of novel constrained homocholine analogues.     

Indium triflate mediated acetalization of aldehydes and ketones

Aldehydes and ketones are rapidly transformed into either acyclic or cyclic acetals at room temperature in high yields and in very short reaction times using catalytic quantities of indium triflate, in contrast to previous reports.     

Ruthenium-catalyzed annulation of aromatic ketones with internal alkynes: A reliable route to substituted naphthalene derivatives

We report herein the preparation of polysubstituted naphthalene derivatives by the ruthenium-catalyzed benzannulation reaction of aromatic ketones with internal alkynes. This method (1) forms two new carbon-carbon bonds in one single step, (2) accommodates a variety of functional groups, and (3) undergoes mild reaction conditions.