The regiospecific acylation of fulvenes

1-Acylated fulvenes were the only monoketones formed by treatment of fulvenes with methyl iodide, carbon monoxide, catalytic quantities of benzyltriethylammonium chloride and dicobalt octacarbonyl, in a two-phase system [5N NaOH/C₆H₆].     

Biscyanines with unconjugated chromophores from 2,4-dimethylthiazole and lepidine derivatives

Bisquaternary salts in which the hydrogen atoms of the heterocyclic rings are bonded by polymethylene chains of different lengths were synthesized from lepidine and 2,4-di-methylthiazole. Biscyanine dyes were obtained from salts with an active methyl group. The absorption spectra of the dyes were investigated. It is shown that the unconjugated chromophores linked by a saturated chain of short length have a mutual effect upon one another, and this interaction decreases rapidly as the length of the isolating group increases.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1489–1492, November, 1974.     

The acylation of 5H-2,3-benzodiazepines

The products obtained from the acylation of 4-phenyl-5$\text{H}$-2,3-benzodiazepine (5) are strongly dependent on the nature of the acylating agent and the reaction conditions. Reaction with acid anhydrides followed by a nucleophile gives the 1-substituted 2-acylbenzodiazepines (10) and (11) while reaction with acyl or sulphonyl halides either induces a ring transformation to give the 3-phenylisquinoline $\text{N}$-imine salts (12) or results in the formation of the acylated dimer (13) $\text{via}$ a dehydrochlorinated intermediate (15).     

The selective reductive acylation of a-keto imines

Reaction of α-keto imines with the $\text{in}$$\text{situ}$ generated acetylcobalt tetracarbonyl occurs only at the carbon—nitrogen double bond to give β-keto amides. An unexpected by-product was formed in several instances.     

Synthesis of lepidine and its derivatives from aromatic amines and mannich bases

The synthesis of lepidine from aniline and 4-diethyl-amino-2-butanone has been carried out in two separate stages under the optimum conditions for each stage.     

The use of sulfines in nucleophilic acylation reactions

The thiophilic addition of MeLi and BuLi to aromatic alkylthio- and arylthio sulfines has been studied. The resulting dithioacetal monoxides are isolated in high yields. Reactions of MeLi with aromatic arylsulphinyland arylsulfonyl sulfines give the corresponding dithioacetal di- and trioxidcs. Acid treatment of dithioacetal monoxides results in aromatic aldehydes. The nucleophilic acylation of the acylanion equivalents obtained from sulfines is investigated. Alkylation of the dithioacetal monoxide anions, prepared in situ from MeLi and sulflnes of the type Ar(RS)CSO. with primary alkyl halides leads to dithioketal monoxide which upon acidolysis under anhydrous conditions are converted into vinylsulfides. The mechanism of the formation of the vinyl sulfides is discussed. The acylanion equivalents are acylated with benzoylchloride, CO₂ and benzaldehyde. The use of Cu¹ and 18-crown-6 as a catalyst appears to be crucial in some reactions. Michael additions of the dithioacetal monoxides to acrylonitrile are described.     

The first intermolecular Friedel-Crafts acylation with beta-lactams

The first intermolecular Friedel-Crafts acylation of a variety of aromatic substrates with azetidinones is described. The Friedel-Crafts acylations are performed under very mild conditions, using trifluoromethanesulfonic acid to produce beta-amino aromatic ketones in excellent yields.     

Lanthanide triflate-catalyzed arene acylation. Relation to classical Friedel-Crafts acylation

Lanthanide trifluoromethanesulfonates, Ln(OTf) 3 (OTf (-) = trifluoromethanesulfonate), serve as effective precatalysts for the rapid, regioselective, intermolecular acylation of activated arenes. This contribution probes mechanism and metal ionic radius effects in the catalytic lanthanide triflate-mediated acylation of anisole with acetic anhydride. Kinetic studies of Ln(OTf) 3 (Ln = La, Eu, Yb, Lu)-mediated anisole acylation with acetic anhydride in nitromethane reveal the rate law nu approximately k 3 [Ln (3+)] (1)[acetic anhydride] (1)[anisole] (1). Eyring and Arrhenius analyses yield Delta H++ = 12.9 (4) kcal.mol (-1), Delta S++ = -44.8 (1.3) e.u., and E a = 13.1 (4) kcal.mol (-1) for Ln = Yb, with the negative Delta S++ implying a highly organized transition state. The observed primary kinetic isotope effect of k H/ k D = 2.6 +/- 0.15 is consistent with arene C-H bond scission in the turnover-limiting step. The proposed catalytic pathway involves precatalyst formation via interaction of Ln(OTf) 3 with acetic anhydride, followed by Ln (3+)-anisole pi-complexation, substrate-electrophile sigma-complex formation, and turnover-limiting C-H bond scission. Lanthanide size effects on turnover frequencies are consistent with a transition state lacking significant ionic radius-dependent steric constraints. Substrate-Ln (3+) interactions using paramagnetic Gd (3+) and Yb (3+) NMR probes and factors affecting reaction rates such as arene substituent and added LiClO 4 cocatalyst are also explored.     

Synthesis of lepidine and its derivatives from aromatic amines and quaternary salts of Mannich bases

A quaternary salt of 4-(diethylamino)butan-2-one, methyldiethyl-3-ketobutylammonium methyl sulfate, is used as an alkylating agent to synthesize lepidine and 1-phenyllepidine salts. The method gives good yields, under mild conditions, of lepidine and 1-phenyllepidine perchlorate. An intermediate product is isolated, and a reaction mechanism suggested.     

Exhaustive acylation of dihydroquercetin

Reaction of dihydroquercetin with acid chlorides of higher and functionalized carboxylic acids was studied with the purpose of creation of new pharmaceuticals.     

The stabilization of electrospun chitosan nanofibers by reversible acylation

Chitosan nanofibers fabricated by electrospinning are contaminated by acidic anions from the acid spinning solution, leading to instability of the nanofibers in aqueous solutions, and the traditional fiber treatment method will also lead to the deterioration of the nanostructure. Here we demonstrate a novel approach to removing the acidic anions with full preservation of the nanofibrous structure. The as-spun nanofibers are first protected (stabilized) by reversible acylation. Second, contaminants are then eliminated by hydrolysis; finally, acylation is reversed. Chemical analysis showed the removal of the acidic anions and the graft and removal of acyl groups. Morphological analysis showed that the reversibly acylated fibers had diameters <150 nm and nanofiber structure was maintained after immersion in aqueous solution. The membranes also were compatible with bone cells in culture. The resultant pure chitosan nanofibers show excellent stability in aqueous solution and exhibit broad potential in biomedical applications.     

The azo coupling of 1-aryl quaternary salts of lepidine and quinaldine and some properties of the reaction products

A series of formazans has been obtained by the coupling of 1-aryllepidinium and 1-arylquinaldinium salts with diazonium salts. The formazans have been converted by oxidation into tetrazolium salts and by the action of acids into benzotriazines. The absorption spectra in the visible region have been measured in neutral, alkaline, and acid media.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 8, pp. 1104–1111, August, 1970.     

Regioselective acylation of aminoresorcinarenes

The acid catalyzed hydrolytic cleavage of the oxazine rings in the readily available tetraoxazine derivatives of resorcinarenes results in tetraaminoresorcinarenes. A similar process applied to C₂-symmetrical bisoxazine resorcinarene tetratosylates affords C_2v-symmetrical resorcinarenediamines. The mild acylation of these resorcinareneamines with BOC-anhydride or para-nitrophenyl ester proceeds selectively at the nitrogen atoms without affecting the hydroxyl groups. Most of the resulting resorcinareneamides are thus obtained in preparative yields and can be easily purified by simple crystallizations. In the crystalline state the compounds obtained are found to bind chloride anions through hydrogen bonds and electrostatic interactions and to display a chiral arrangement of hydrogen bonded functional groups at the wide rim of the macrocycle.     

Friedel-Crafts acylation with amides

Friedel-Crafts acylation has been known since the 1870s, and it is an important organic synthetic reaction leading to aromatic ketone products. Friedel-Crafts acylation is usually performed with carboxylic acid chlorides or anhydrides, while amides are generally not useful substrates in these reactions. Despite being the least reactive carboxylic acid derivative, we have found a series of amides capable of providing aromatic ketones in good yields (55-96%, 17 examples). We propose a mechanism involving diminished C-N resonance through superelectrophilic activation and subsequent cleavage to acyl cations.