Ketones saturated heterocyclic

The vast majority of studies on fully saturated systems involve 1,3-dioxanes and their application as protecting groups for ketones or 1,3-diols <2006JOC6258>. In this overview, the focus on fully saturated heterocycles is on the nondestructive reactivity of fully saturated 1,3-heterocycles although some ring-opening reactions are also presented. 

The reaction is applicable to saturated and unsaturated methyl ketones of the aliphatic and alicyclic series, to aryl methyl ketones, and to methyl ketones of heterocyclic aromatic compounds. 

Saturated heterocyclic ketones are also good substrates for mixed aldol condensations with aromatic aldehydes. Again, a selection of high-yielding examples is presented in equations (76)-(80). These... 

A tridentate phosphine-diamine ligand 96 together with [IrCl(COD)]2 constituted an efficient catalyst system for TH of cycloalkyl and saturated heterocyclic ketones with propan-2-ol at room temperature [90]. For instance, cyclohexyl phenyl ketone was reduced using 0.1 mol% of the in situ-formed iridium catalyst reaching a 94 % conversion in 30 min and giving the corresponding alcohol in 95 % ee. 

Silver(I) carbonate functioned as an cooxidant with TEMPO. Tricyclohexylphosphine was employed to suppress homocoupling between heteroarenes. Substituted thiophenes, furans, and indoles could be selectively olefinated (C5-alkenylation for thiophenes and furans, C3-alkenylation for indoles, E/Z > 99 1). Unsubstituted thiophenes produced poor yields (24%) however, formyl, acetyl, and ketyl substituents were well tolerated. For electron-deficient substrates, tricyclohexylphosphine was reduced to 10 mol % to achieve good conversions. A variety of ketones could be employed using 2-methyl thiophene as a coupling partner. A related methodology employing saturated ketones and heterocyclic carboxylic acids via a Pd-catalyzed decarboxylative process was also reported (eq 44). ... 

The electrolysis of asymmetric ketones 43 led to the formation of isomers and stereoisomers. Kinetic measurements for the formation of ketimine 43 in saturated ammoniacal methanol indicated that at least 12 h of the reaction time were required to reach the equilibrium in which approximately 40% of 42 was converted into the ketimine 43. However, the electrolysis was completed within 2.5 h and the products 44 were isolated in 50-76% yields. It seems that the sluggish equilibrium gives a significant concentration of ketimine 43 which is oxidized by the 1 generated at the anode, and the equilibrium is shifted towards formation of the product 44. 2,5-Dihydro-IH-imidazols of type 44, which were unsubstituted on nitrogen, are rare compounds. They can be hydrolyzed with hydrochloric acid to afford the corresponding a-amino ketones as versatile synthetic intermediates for a wide variety of heterocyclic compounds, that are otherwise difficult to prepare. 

Other commonly occurring chemical groups in essential oils include aromatics such as /3-phenethyl alcohol, eugenol, vanillin, benzaldehyde, cinnamaldehyde, etc heterocyclics such as indole, pyrazines, t hi azoles, etc hydrocarbons (linear, branched, saturated, or unsaturated) oxygenated compounds such as alcohols, acids, aldehydes, ketones, ethers and macrocyclic compounds such as the macrocyclic musks, which can be both saturated and unsaturated,... 

The photoreactions of saturated five-membered heterocycles are generally characterized by initial carbon-heteroatom bond homolysis. Tetrahydro-furans150 and 1,3-dioxolans151 behave in this way, and the major photoproducts of 2,2-dimethyl-1,3-dioxolan, for example, are acetone, propyl acetate, ethylene, acetaldehyde, methyl acetate, and oxiran. The vinyltetrahy-drofuran (180) is converted on irradiation in methanol to the ketal (181) and the ketone (182) by way of a Wagner-Meerwein shift in the carbocation... 

This is the strategy followed in most thiazole syntheses. The regioselectivity issue is which way the reagents combine. There are two possibilities the sulfur could attack either the ketone or the saturated carbon atom as can the nitrogen. But sulfur is excellent at Sn2 reactions while nitrogen is better at addition to carbonyls. So 27 and not 35 is the product. No intermediates are isolated once either the C-S or the C-N bond is formed, cyclisation and aromatisation are fast. This means that aromatic heterocycles are easier to make than the non-aromatic ones. 

Effect of Phospholipids on Reaction Volatiles. As would be expected, the inclusion of phospholipids in the reaction mixtures produced many volatiles derived from lipid degradation these included hydrocarbons, alkylfurans, saturated and unsaturated alcohols, aldehydes and ketones. However, two other important observations were made. First, the concentrations of most of the hetero- cyclics, formed by the amino acid + ribose Maillard reaction, were reduced. For most of the major volatiles this reduction was of the order of 40 - 50%, but in the case of thiophenethiol and methyl- furanthiol the reduction was over 65%. This appears to support the findings that in meat and coconut, lipids exert a quenching effect on the amount of heterocyclic compounds formed in Maillard reactions during heat treatment (11,12). Second, and perhaps more important, the addition of phospholipid to the reaction mixtures resulted in the production of large amounts of compounds derived from the interaction of the lipid or its degradation products with Maillard reaction intermediates. 

Key to method (A) exchange reaction with tin heterocycle (B) hydride addition to diyne (C) oxidation of saturated ketone (D) bromination-dehydrobromination by pyrolysis (E) reaction of RLi or ArLi with exocyclic M-Cl of preformed diene (F) ring expansion reaction from cyclopentadiene derivative (G) LiAlHi reduction of exocyclic M-Cl (H) carbene insertion into five-membered cyclo-pentadiene derivative. Doering-Hoffman method (I) 1,6-cycloaddition of GeCU. 

The acetal (144) has been converted by the Vilsmeier reagent into the methoxy-enal (145), from which a variety of heterocyclic compounds has been obtained. The enal will condense with reactive methylene compounds, and reacts with lithium alkyls to give, after hydrolysis, ajS-unsaturated ketones of general structure (146) these are reducible to saturated ketones, which would otherwise be available only by Diels-Alder addition of dienophiles that are difficult to obtain, to thebaine. ... 

We have reported a number of cyclization reactions. The one- and two-N containing five and six-membered, saturated and unsaturated heterocycles were synthesized from C to Cs aliphatics like alcohols, aldehydes, ketones, in presence of ammonia and other amines [11-33]. For example, 3,5-lutidine was synthesized from propionaldehyde or propanol, formaldehyde and ammonia over modified ZSM-5 catalysts. The yield of 3,5-lutidine was in the range of 40 to 65 wt% at 60-90% conversion of propionaldehyde over modified ZSM-5 catalysts at 400 C. In the reaction of ethanol, formaldehyde and ammonia over ZSM-5 catalyst pyridine and picolines were obtained. The reaction route or mechanism is shown in Fig. 2 and 3. In the reaction of acetaldehyde, formaldehyde and ammonia over ZSM-5 pyridine and 3-Picoline were obtained. On the other hand, 2- and 4-Picolines were obtained in the reaction of acetaldehyde and ammonia. 

The photoionisation detector (PID) is used for the selective determination of aromatic hydrocarbons and unsaturated compounds such as aliphatics, aromatics, ketones, esters, aldehydes, amines, heterocyclics and some organometallics. It is relatively insensitive to saturated hydrocarbons and halocarbons. This device uses ultraviolet light as a means of ionising the analytes exiting the GC column and the ions produced by this process... 

---