Penten-2-ol

Submitted by L. A. Brooks and H. R. Snyder. Checked by Nathan L. Drake and W. Mayo Smith. 

Tetrahydrofurjuryl chloride. In a 2-1. three-necked flask, fitted with a mechanical stirrer, a dropping funnel, and a thermometer, are placed 408 g. (4 moles) of freshly distilled tetra-hydrofurfuryl alcohol (Note 1) and 348 g. (4.4 moles) of pyridine. To the rapidly stirred mixture which is cooled in an ice bath, 500 g. (4.2 moles) of freshly distilled thionyl chloride (Note 1) is added from the dropping funnel at the rate of 3-5 drops per second. When one-third to one-half of the thionyl chloride has been added, a pasty crystalline mass begins to separate and the temperature begins to rise rapidly. The temperature should not be allowed to go above 60°. As more thionyl chloride is added the mass redissolves and a dark brown liquid forms. When the addition is complete, the bath is removed and the mixture is stirred for 3-4 hours. The liquid (or the slurry, if some crystalli- 

Undistilled commercial thionyl chloride and Eastman Practical tetrahydrofurfuryl alcohol may be used, but the yields are slightly lower (65-70%). 

The checkers found it easier to separate the ethereal extract from the residue when the mixture was in a large separatory funnel. 

The yield will be low if extraction is incomplete. It is advisable to stir with a heavy glass rod and break up any lumps that have formed. 

Checked by Homer Adkins, B. W. Winner, John Woods, 

At the end of this time, when almost all the magnesium has reacted, the Dry Ice cold finger is replaced with a water condenser and the gas delivery tube with a dropping funnel. A solution of 142 g. (2.02 moles) of freshly distilled crotonaldehyde in 300 ml. of dry ether is added dropwise while the reaction mixture is stirred vigorously and cooled. The reaction mixture is allowed to stand at room temperature for 1 hour. 

The Grignard addition compound is decomposed by adding 435 ml. of a saturated ammonium chloride solution (Note 5) dropwise, with vigorous stirring, to the thoroughly cooled reaction mixture. A dense white precipitate, too heavy to be stirred mechanically, forms and settles to the bottom of the flask. After the reaction mixture has been allowed to stand for 1 hour, the ether solution is poured off and the precipitate washed by decantation with two 300-ml. portions of ether. 

The ether is removed by distillation, and the residual 3-pen-ten-2-ol is distilled through a short column (Note 6) at atmospheric pressure. The yield of material boiling at 119-121° is 140-150 g. (81-86%). Pure 3-penten-2-ol boils at approximately 120°/740 mm. 

A Hershberg type of stirrer 1 is preferred. The submitter used a stirrer of tantalum with a mercury seal the checkers used a Nichrome stirrer in a simple rubber seal.  

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Results of oxidation of unsaturated alcohols are shown in Table 3. Both 2-penten-1 -ol and 3-methyl-2-buten-1 -ol exhibited higher reactivity than cyclohexene. A decrease around 20-50% in catalytic activity of organically functionalized samples has been observed. This is probably due to the inhibition of access of the rather hydrophilic substrates to the Ti-active sites surrounded by the organic groups of increased hydrophobicity. It is noteworthy that the epoxidation was favorable for the organically functionalized samples whereas the alcohol oxidation was retarded. 

Suppose you were given unlabeled bottles, each of which is known to contain one of the following compounds 1-pentanol, 2-pentanol, 2-methyl-2-butanol, 3-penten-1-ol, 4-pentyn-1-ol, 1-butoxybutane, and 1-pentyl acetate. Explain how you could use simple chemical tests (test-tube reactions only) to identify the contents of each bottle. 

Benzyl-5-phenyl-2-pentenal 2-Benzyl-5-phenyl-2-penten-1 -ol... 

Add a solution of the chiral sulfonamide and ( )-5-phenyl-2-penten-1-ol in dichloromethane (200 mL) at room temperature. 

The scope of this approach was widened by the observation of excellent enantioselectivities in intermolecular [2+ 2]-photocycloaddition reactions with various alkenes [62,71]. In the presence of an excess amount of alkene, 4-me thoxy-2-quinolone (57) was converted with high chemo- and regioselectivity to the exo and endo cyclobutanes 59 and 60. With 4-penten-1-ol (58a), allyl acetate (58b), methyl acrylate (58c), and vinyl acetate (58d), the exo diastereomers 59a-d were formed with high simple diastereoselectivity and in high yields (80-89%), Under optimized irradiation conditions (2.4 eq. of host 44 or ent-44, — 60°C), high enantiomeric excesses were achieved in all instances, as depicted in Scheme 22. These enantiomeric excesses are unprecedented for an intermolecular photochemical reaction. 

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