Methyl with cyclopentene

One mole of isoprene reacted with one mole of acetoacetate by using a bidentate phosphine as ligand (56). Reaction of 2,3-dimethylbutadiene with acetoacetate was carried out by using PdCl2 in the presence of sodium phenoxide. When PPh3 was used, a 1 2 adduct was obtained. On the other hand, use of P-phenyl-l-phospha-3-methyl-3-cyclopentene (105) at 100°C caused the 1 1 addition to give 3-carbomethoxy-5,6-dimethyl-5-hepten-2-one (106), from which 5,6-dimethyl-5-hepten-2-one (107) was formed. This compound is the useful intermediate for a-irone synthesis (96). 

The product, l,4-diacetoxy-2-allyl-3-methyl-2-cyclopentene, obtained (45% current efficiency) from 2-allyl-3-methyl-l,3-cyclopentadiene through anodic oxidation with carbon rod anode in acetic acid is successfully used as a starting compound in the synthesis of allethrolone as shown in equation 23. 

The submitters report that dimethyl 3-cyclopentene-1,1-dicarboxylate (with <1% of the vinyl isomer)2 3 can be isolated at this stage in 92% yield and then transformed to methyl 3-cyclopentene-1-carboxylate4 with lithium chloride in wet dimethyl sulfoxide (DMSO)5 in 85% yield. 

In fluorosulfonic acid the anodic oxidation of cyclohexane in the presence of different acids (RCO2H) leads to a single product with a rearranged carbon skeleton, a 1-acyl-2-methyl-1-cyclopentene (1) in 50 to 60% yield (Eq. 2) [7, 8]. Also other alkanes have been converted at a smooth platinum anode into the corresponding a,-unsaturated ketones in 42 to 71% yield (Table 1) [8, 9]. Product formation is proposed to occur by oxidation of the hydrocarbon to a carbocation (Eq. 1 and Scheme 1) that rearranges and gets deprotonated to an alkene, which subsequently reacts with an acylium cation from the carboxylic acid to afford the a-unsaturated ketone (1) (Eq. 2) [8-10]. In the absence of acetic acid, for example, in fluorosulfonic acid/sodium... 

Trans-1 -allyl-2-(trimethylsilyl)cyclopentane and trans-1 -allyl-2-(trimethylsilyl)-cyclohexane are formed from the reaction of la with cyclopentene and cyclohexene, respectively. A second allylsilylation reaction of these compounds with la also gives unusual allylsilylation products, 7-cyclopent-l-enyl-2,2-dimethyl-4-(trimethylsilyl-methyl)-2-silaheptane (30%) and 4-((cyclohex-l-enyl)methyl)-2,2,8,8-tetramethyl-2,8-disilanonane (39%). As observed in the allylsilylation of 4-(trimethylsilyl-methyl)-l-alkenes, these products are likely formed via intramolecular silyl rearrangements. In this case, the results strongly suggest that a 1,5-silyl shift and... 

A plausible mechanism involves the reaction of the dihydride precursor with t-butylethylene to the 14-e complex [Ir(C6H3-2,6 CH2P-f-Bu2 2)]> which undergoes the oxidative-addition reaction of the alcohol to afford a hydride alkoxide complex. Further /i-hydride ehmination gives the alde-hyde/ketone and regenerates the dihydride active species [55]. In the particular case of 2,5-hexanediol as the substrate, the product is the cycHc ketone 3-methyl-2-cyclopenten-l-one. The formation of this ketone involves the oxidation of both OH groups to 2,5-hexanedione followed by an internal aldol reaction and further oxidation as in the final step of a Robinson annotation reaction [56]. 

Petrov and Shchekin (297) showed that below the cracking temperature (250-316°C.) cyclohexene undergoes over silica-alumina hydrogen disproportionation and dimerization. Identical results were obtained from 1-methyl-l-cyclopentene. Ring expansion of lower alkylated cyclopentanes occurs simultaneously with polymerization. However, no bicyclic compounds with similar rings were formed. 

D. 2-Methyl-3-[(phenylsulfonyl)methyll-2-cyclopenten-1 -one. In aflame-dried, 1-L, round-bottomed flask equipped with an addition funnel under a nitrogen atmosphere are placed 20.0 g (58.8 mmol) of 2,3-dibromo-1-(phenylsulfonyl)-1-propene and 7.0 mL (60.0 mmol) of 3-methyl-2,4-pentanedione in 300 mL of methanol (Note 8). The flask is cooled using an ice-water bath. To this mixture is added 140 mL... 

Vinylcarbene is also regarded as an intermediate in the catalytic isomerization of cyclopropene in the presence of [CuCl P(OPh)3 ]. 3-Methyl-3-cyclopropylcyclopropene (83a) and 3,3 dicyclo-propylcyclopropene (83b) react with cyclopentene derivatives under die influence of CuCl/P(OPh)3 to yield cntfo-vinylcyclopropane derivatives (84 equation 37) in 55-72% yields. 3-Methoxycarbonyl-l-propylcyclopropene also reacts with noibomadiene in the presence of CuCl to give the corresponding vinylcarbene adducts in 60% yield. 

In addition, condensation of 2,4-pentanedione with 1,2-dibromoethane only affords 1,1-diacetylcyclopropane (421) in 20% yield, together with l,l,3-triacetyl-2-methyl-2-cyclopentene (423) formed via further attack of the 2,4-pentanedione carbanion on 421 and ring-closure of tetraacetylbutane (422) (equation 138). Better yields have been... 

Figure 5.2.11. Cellulose pyrolysate obtained at 59(P C and separated on a methyl silicone with 5% phenyl silicone type column. 1 acetic anhydride, 2 pentanal, 3 2-hydroxybutanedialdehyde, 4 1,4-dioxadiene, 5 tetrahydro-2-furanmethanol, 6 2-(hydroxymethyl)-furan, 7 3-methyl-2-hexanone, 8 2-methoxy-2,3-dihydrofuran, 9 2(5H)-furanone, 10 1-acetyloxypropan-2-one, 11 hydroxycyclopentenone, 12 5-methylfurfural, 13 2,3-dihydro-5-methylfuran-2-one, 14 1-cyclopentylethanone, 15 2-hydroxy-3-methyl-2-cyclopenten-1-one, 16 3,5-dimethylcyclopentan-1,2-dione, 17 unknown, 18 3-ethyl-2,4(3H,5H)-furandione, 19 6-methyl-1,4-dioxaspiro[2,4]heptan-5-one, 20 1-hydroxy-3,6-dioxabicyclo[3.2.1]octan-2-one, 21 1,4 3,6-dianhydro-a-D-glucopyranose, 22 5-(hydroxymethyl)-furfural, 23 4-cyclopenten-1,2,3-triol, 24 5-ethyl-3-hydroxy-4-methyl-tetrahydrofuran-2-one, 25 levoglucosan, 26 1,6-anhydro-p-D-glucofuranose.

Flavourings that are useful for aromatising bakery and chocolate food products can be made from sulphur-free amino acids by the reaction with cyclic ketones (Fig. 3.36) such as 4-hydroxy-2,5-dimethyl-3(2//)-furanone (26), maltol (63) or 2-hydroxy-3-methyl-2-cyclopenten-l-one (64, cyclotene) [109]. Amino acids of special interest are leucine, valine, proline and hydroxyproline. The reaction is carried out favourably in fat or propylene glycol. 

Methylation with methyl Grignard reagent affords 3-trimethylsilylcyclopent-l-ene, which is a versatile reagent for the regiospecific introduction of the cyclopentene skeleton in organic synthesis . 

Valerianine (13) was synthesized in racemic form by Franck and coworkers (75) in 1970. Diene condensation of 5-methyl-l-cyclopentene carboxaldehyde (175) with 1,3-dimethoxy propene (176) afforded the tetrahydropyranyl ether 177, which, on acid hydrolysis, afforded 9-methoxy-iridodial (178). This compound was not isolated, but was converted directly to ( )-valerianine 13) with either Fe(NH4)2S04 or NH2OH (Scheme 8)... 

Nishimura O., Mihara S. and Shibamoto K. (1980) Compounds produced by the reaction of 2-hydroxy-3-methyl-2-cyclopenten-l-one with ammonia and hydrogen sulfide. J. Agric. Food Chem. 28, 39 43. 

Acetoxy-2- (2-butenyl) - 5-carbethoxy - 3 -methyl - 2 - cyclopenten-l-one covered -with coned, aq. NH3, allowed to stand for 3 days with frequent shaking —> 2-(2-butenyl)-5-carbamyl-5-hydroxy-2-eyclopenten-l-one (Y 80%) boiled 1 hr. with 10% H2S04 2-(2-butenyl)-5-hydroxy-... 

A. 7, -Diohloro-l-methylbieyclo[3.2.0]heptan-6-one. A 500-mL, two-necked, round-bottomed flask 1s equipped with a Teflon-covered magnetic stirring bar, a 250-mL pressure-equalizing addition funnel topped with a gas inlet, and a condenser connected to a Nujol-filled bubbler (Note 1). The system 1s flushed with nitrogen (Note 2). The flask 1s then charged with 10.0 g (ca. 150 nmol) of zinc-copper couple (Note 3), 200 mL of anhydrous ether (Note 4), and 10.5 mL (8.2 g, 100 mmol) of 1-methyl-1-cyclopentene (Note 5) and the addition funnel is filled with a solution of 13.4 mL (21.8 g, 120 mmol) of trlchloroacetyl chloride (Note 5) and 11.2 mL (18.4 g, 120 mmol) of phosphorus oxychloride (Note 6) 1n 100 mL of anhydrous ether. Magnetic... 

The pressure effect on phptochemical cycloadditions was also investigated in a very elaborate procedure [58]. For this purpose an optical cell with sapphire windows and a laser containing a Xe/Vi/Hi gas mixture was used. Irradiation of cy-clopentenone (111) with substituents of different size at C-3 ranging from hydrogen to methyl, ipropyl and t-butyl, with cyclopentene (112) and 3,3-dimethylbutene (115) gave the diastereomeric cycloadducts 113-117 (Scheme 8.27). 

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