5- Hydroxy-2-pentanone

Hydrogenation of 2-methylfuran in the presence of water leads to the formation of 5-hydroxy-2-pentanone and 1,4-pentanediol.189 190 Schniepp et al. obtained 5-hy-droxy-2-pentanone in 25-35% yields or 1,4-pentanediol in 50-60% yields, together with 2-methylterahydrofuran, by hydrogenation of 2-methylfuran in the presence of water and formic acid in concentrations of 0.01-0.10 wt% of the reaction mixture using a reduced Ni-on-Celite as catalyst (eq. 12.97).190... 

Londergan et al. could obtain 5-hydroxy-2-pentanone in a 75% yield by hydrogenating 2-methylfuran in a mixture of acetone and 0.2M hydrochloric acid using 5% Pd-C as catalyst (eq. 12.98).191... 

It has been demonstrated that the 4,5-dihydro-2-methylfuran, formed as an intermediate, hydrolyzes to 5-hydroxy-2-pentanone through the reaction sequence shown in Scheme 12.25.189,190,192 On the other hand, 5-hydroxy-2-pentanone was cyclodehy-drated to give 4,5-dihydro-2-methylfuran in yields of 86% or more in a continuous process in the presence of phosphoric acid (Scheme 12.25). Furan-2-carboxylic acid (2-furoic acid) was hydrogenated to the corresponding tetrahydro derivative in water over Skita s colloidal palladium at room temperature193 or over Raney Ni in ammo-niacal water at 130-150°C and 0.93 MPa H2 (eq. 12.99)194 or as its sodium salt in water at 110°C and 5.2 MPa H2.195... 

In the case of 5-hydroxy-2-pentanone, there is a slight preference for the open-... 

Various derivatives of fiuan and pyran are cleaved to give open-chain di- and poly-functional compounds. Fission to give dihalides, halo alcohols, and halo esters is described elsewhere (method 34). Hydrogenation and hydrogenolysis reactions lead to hydroxy compounds, as in the preparation of 5-hydroxy-2-pentanone and 1,4-pentanediol from methyl-... 

Dehydrogenation of 1,4-pentanediol over a copper chromite catalyst in the liquid phase yields the corresponding hydroxy ketone, 5-hydroxy-2-pentanone (30%). ... 

Application of the general strategy to the Grignard addition of CH3MgCl to 5-hydroxy-2-pentanone is illustrated in Figure 20.7. 

Devise a synthesis of each compound from 5-hydroxy-2-pentanone (CH3COCH2CH2CH2OH) as starting material. You may also use alcohols having three or fewer carbons and any required organic or inorganic reagents. 

A study by Sobs has demonstrated that the formation of 5-hydroxy-2-pentanone in the hydrogenation of 2-methylfuran in aqueous alkaline media does not involve 2-methyl-4,5-dihydrofuran as an intermediate, as was earlier believed. Sobs proposes that 2-methylfuran is hydrated on the catalyst surface (Pd/C) to give 2-hydroxy-2-methyl-2,5-dihydrofuran, which is hydrogenated to afford eventually 5-hydroxy-2-pentanone (Scheme 2). ... 

Intramolecular dehydration of y-hydroxyketones.2 When y-hydroxy ketones are heated to about 150° with DCC, water is eliminated with formation of a cyclopropane ring. For example, 5-hydroxy-2-pentanone (1) is transformed into (3) in 80% yield. In the suggested mechanism, (2) is proposed as an intermediate. The reaction is noteworthy because dehydration is accompanied by formation of a carbon-carbon bond. 

Another interesting application is the use of the Kabachnik-Fields reaction for the preparation of cyclic aminophosphonates-l,2-oxaphospholanes and 1,2-oxaphosphori-nanes [37]. 3-Amino-3-methyl-2-ethoxy-2-oxo-l,2-oxaphosphorinane is obtained by aminophosphonylation of 5-hydroxy-2-pentanone. 

Give the reaction scheme, showing the products formed (before hydrolysis), when one equivalent of ethylmagne-sium bromide is treated with one equivalent of 5-hydroxy-2-pentanone. Does addition of two equivalents of the Grignard reagent to this ketone yield a different product(s) If so, give the structure (s). 

For example, the synthesis of receptor 7, a caUxpyrrole with an isophthalate strap, is shown in Scheme This compound was synthesized by condensation of 5-hydroxy-2-pentanone with pyrrole in the presence of an acid catalyst to afford the dipyrromelhane. Isophthaloyl dichloride was made to react with 2 equivalents of Ihe dipyrromethane to afford the bis-dipyrromethane that was condensed with... 

For the thiazole (Scheme 12.90), ethyl acetoacetate was treated with ethylene oxide (oxirane) in the presence of sodium ethoxide to produce the corresponding furanone, which yielded a chloride on treatment with thionyl chloride. The chlorine served to remove the only active proton remaining and introduced the future leaving group. Thus, hydrolysis of the lactone yielded 3-chloro-5-hydroxy-2-pentanone, which, on treatment with thioformamide, provided a modest yield of the 4-methyl-5-(P-hydroxyethyl)thiazole. 

Suppose, for example, that you wanted to add methylmagnesium chloride (CHsMgCl) to the carbonyl group of 5-hydroxy-2-pentanone to form a diol. Nucleophilic addition will not occur with this substrate. Instead, because Grignard reagents are strong bases and proton transfer reactions are fast, CH3MgCI removes the O-H proton before nucleophilic addition takes place. 

In Step [1], the OH proton in 5-hydroxy-2-pentanone is replaced with a protecting group, written as PG. Because the product of Step [1] no longer has an OH proton, it can now undergo nucleophilic addition. 

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