2.4- Pentanedione, 3- methylene

Trimethyl phosphite (11.3 g, 0.091 mol) was added to a solution of 3-benzylidene-2,4-pentanedione (16.35 g, 0.091 mol) in dry methylene chloride. The solution was maintained under nitrogen for 24 h at 20°C and for an additional 5 h at 40°C. After this time, the solvent was evaporated, and the residue was dissolved in hexane. These actions were performed in the absence of moisture. The clear hexane solution was seeded with a crystal of the pure crystalline product (obtained by crystallization from hexane by standing for 2 weeks at 0°C), and after 8 h at 0°C the crystals precipitated yielding pure 2,2,2-tri-methoxy-3-phenyl-4-acetyl-5-methyl-A4-oxaphospholene (25.12 g, 88.4%) of mp 48-51°C. 

Figure 4. Profiles of volatiles for high-quality peanuts, raw and roasted (1) ethanol (2) pentane (3) 2-propanol (4) acetone (5) methylene chloride (6) methyl acetate (7) 2-methylpropanal (8) diacetyl (9) 3-methylbutanal (10) 2-methyl-butanal (11) 2,3-pentanedione (12) S-methylpyrrole (13) toluene (14) hexanal (15) 2-methylpyrazine (16) xylene (17) 2-heptanone (18) 2,5-dimethylpyrazine (19) 2-pentylfuran (20) 2-ethyl-5-methylpyrazine (21) 2-ethyl-3,6-dimethylpyra-zine (22) phenylacetaldehyde.

For such hex-3-enopyranosid-2-uloses as 127 or 129, reaction with lithium dimethylcuprate,261 or with anions of malonic ester-type, methylene components in the presence of bis(2,4-pentanedionate)-Ni(II) catalyst,263 affords, in each case, the 1,4-addition products (128 and 130, respectively), in which the branching group is in the axial orientation. The methyl-branched pyranosides 126 and 128, readily accessible in this way, have been of use as chiral precursors for the synthesis of multistria-tins.264-285... 

A mixture containing 3-cyanbenzaldehyde, 2,4-pentanedione, piperidine and acetic acid in toluene was refluxed for some hours. After standing over night at room temperature the crystals were filtered and washed with toluene and dried. There was obtained the 3-[(2-cyanophenyl)methylene]-2,4-pentanedione. 

Addition of active methylene compounds to butadiene has been catalyzed by complexes of the nickel triad. A catalyst mixture of Ni(acac)2, PPr(OR )2, and borohydride was effective for the addition of R1R2CH2 (Ri = Ph, R2 = COCH3 Ri = Ph, R2 = CN Ri = Ra = COgEt Ri = COCH3, Rg = COgEt) to butadiene 26). Both Pd(0) and Pd(II) complexes are effective as catalysts for the addition of active methylene compounds such as 2,4-pentanedione and ethyl acetoacetate to butadiene 177, 269). Several products were obtained from these reactions since both the 1 1 and 1 2 addition occurred. 

To test the volatile heterocyclic conq)ounds formation under low temperature condition, 0.01 mol of one of the following carbonyl compounds including a-hydroxyketones (3-hydroxy-2-butanone, 0.88 g l-hydroxy-2-propanone, 0.74 g l-hydroxy-2-butanone 0.88g) and a-dicarbonyls (2,3-butanedione, 0.86 g 2,3-pentanedione 1.00 g) and 0.02 mol of ammonium sulfide (20% wt/wt solution in water) were dissolved in 25 mL distilled water and reacted at 25°C for 2 hours. Immediately follow the reactions, the mixtures were cooled and extracted with methylene chloride three times, dried over anhydrous sodium sulfate, and then concentrated under a stream of N2 for further GC and GC/MS analyses. 

Diethoxyphosphinyl)methylene ]-2,4-pentanedione [diethyl (2-acetyl-3-oxo-2-butenyl)-phosphonate] (14) A solution of the enol ether (13) (0.1 mole) in ether (100 ml) is treated with a suspension of sodium diethyl phosphite (0.1 mole) in ether (100 ml) and heated under reflux, with stirring, for 2 h. After cooling, the mixture is extracted with 20% hydrochloric acid (19 g). The ethereal phase is dried and freed from ether and unchanged enol ether in a vacuum. Two fractionations of the residue in a vacuum afford the product (61 % crude yield before distillation 80%), b.p. 127°/0.01 mm, D20 1.4622. 

Compounds containing active methylene groups can be alkylated by alcohols with loss of hydrogen from that position. For example, in the presence of boron trifluoride, isopropyl alcohol and ethyl acetoacetate give ethyl 2-iso-propylacetoacetate in 60-70% yield 643 the isopropyl group can be introduced in the same way into acetylacetone (2,4-pentanedione) 644 and reactions of xanthhydrol with malonic esters have also been recorded in the literature.645... 

Alkylation of a 1,3-dicarbonyl compound at a flanking methyl or methylene group instead of at the doubly activated C-2 position does not usually take place to any significant extent. It can be accomplished selectively and in good yield, however, by way of the corresponding dianion, itself prepared from the dicarbonyl compound and two equivalents of a suitable strong base. For example, 2,4-pentanedione 2 is converted into 2,4-nonanedione by reaction at the more-reactive, less-resonance-stabilized carbanion (1.17). ... 

Tris (2,4-pentanedionato) aluminum. See Aluminum acetylacetonate Tris (2,4-pentanedionato) chromium (III). See Chromic acetylacetonate Tris (2,4-pentanedionato) vanadium Tris (pentane-2,4-dionato-0,0 ) vanadium. See Vanadium tris acetyl acetonate Tris (2,4-pentanedione) aluminum. See Aluminum acetylacetonate Tris (phosphonomethyl) amine. See Ami noth methylene phosphonic acid Tris (2-propanol) amine. See Triisopropanolamine... 

The Pd-catalyzed reaction of allylamines with active methylene compounds was first reported in 1970. A,A-Diethylallylamine undergoes reaction with 2,4-pentanedione in the presence of Pd(acac>2 (0.5 mol %) and PPhj (1.5 mol %) at 85 C to give 3-monoallylated and 3,3-bisallylated products in 70% and 20% yields, respectively (Scheme 2). Nickel(O) complexes are found to be a more active catalyst for aUyla-tion. Thus, more than 600 h of turnover frequency was achieved for the allylation of methyl 3-oxobutanoate with A,A-diethylallylamine in DMF at 80 C using Ni(dppb)2 catalyst,... 

Table 1 shows that the nature of the sugar has an impact on the reaction yield with, for instance, a limited interest for arabinose as compared to >ylose, illustrating the importance of the stereochemistry. Moreover, the choice of activated methylenes is also restrictive since only the p-diketone with a simple methyl residue (2,4-pentanedione) gives quantitative yields. 

Condensation of 2,3 4,5-di-O-benzylidene-D-ribose or related aldehydo-D-ribose or -D-glucose derivatives with a number of active methylene compounds, e.g., pentane-2,4-dione, gave the expected Knoevenagel condensation products, which all showed antiviral activity and cytotoxicity the most effective against herpes simplex virus was the ribose-2,4-pentanedione derivative (34) titanium... 

---