5-iodo-l-pentene

Scheme 6.88 (a) Toluene/sealed tube/heat/N-phenylmaleimide (b) sealed tubeAieat/ dimethyl fumarate (c) (i) BuLi/HMPA, (ii) 5-iodo-l-pentene (d) toluene/sealed tube/180-190°C... 

As an example of the use of this methodology in total synthesis, the zirconocene-promoted ring contraction was the key step in the route to (+)-epiafricanol (100) reported by Paquette et al. [78]. Vinyl pyranose 95, obtained from D-glucose in 12 steps, was treated with Cp2Zr in toluene at -78°C and then with boron trifluoride etherate at room temperature, affording vinyl cyclopentane 96 in a 63% yield. Conversion of 96 to ketone 97 with periodinane as the oxidant in the presence of sodium bicarbonate and addition of the lithium derivative to 4,4-dimethyl-5-iodo-l-pentene 98 gave rise to 99. Cyclization of 99 by RCM followed by cyclopropanation finally afforded the desired product 100 (Scheme 3.39). 

Bailey, W. F. Tao, Y. Efficient preparation of vinylcyclopropane by SN cyclization of the organolifhium derived from (E)-5-iodo-l-mefh-oxy-2-pentene. Tetrahedron Lett. 1997, 38, 6157-6158. 

Iodo-4-penten-l-yl 11-Methoxycarbonylundecyl Tellurium (Sodium Borohydride Reduction) Into an argon-purged, 100-m/ flask are placed a magnetic stirrer, 343 mg (0.5 mmol) of bis[ll-methoxycarbonylundecyl] dilellurium and 20 ml of methanol. Excess sodium borohydride is added and the mixture is stirred until it becomes colorless. 354mg (1.1 mmol) of l,5-diiodo-4-pentene are added, the mixture is stirred for 0.5 h, diluted with water, and extracted twice with diethyl ether. The combined diethyl ether extract is washed with water, dried with anhydrous sodium sulfate, and the solvent is evaporated. The residue is dissolved in 2 ml of benzene and chromatographed on a silicic acid column (1 x 20 cm) slurried in petroleum ether. The column is eluted with 200 ml of petroleum ether and then with 400 ml of benzene. Fractions of 20 ml are collected and fractions 16-19 are combined and evaporated yield 130 mg (22%) light yellow oil. 

A three-necked flask was charged with 5-chloro-l-iodo-l-pentene (1.8g, 6.0 mmol) in THF (5 mL) and was cooled to — 100 °C (liquid Nj/ether bath), and n-BuLi (6.3 mmol,... 

A three-necked flask was charged with 5-chloro-l-iodo-l-pentene (1.8 g, 6.0 mmol) in THF (5 mL) and was cooled to — 100°C (liquid N2/ether bath), and n-BuLi (6.3 mmol, 1.6M in hexane) was added over 4 min. The resulting colorless solution was stirred at 0°C for 2min and cooled back to -78 °C. p-Toluenesulfonyl cyanide (0.90g, 5.0 mmol) in THF (5 mL) was added and the reaction mixture was warmed to room temperature and stirred for 3 h. After the usual workup and evaporation of the solvents, the crude residue obtained was purified by flash chromatography (hexane/ether, 10 1), yielding the unsaturated nitrile 10 (466 mg, 72% yield) as a clear oil (100% by GLC analysis and l3C NMR analysis). 

Srivastava, P. C., Knapp, F. F. 1984. [(E)-l-[I-123]iodo-l-penten-5-yl]triphenylphosphonium iodide— Convenient preparation of a potentially useful myocardial perfusion agent. J. Med. Chem. 27 978-981. 

Another type of convertible nucleoside phosphoramidite, a derivative of (5 S)-5 -C-(5-bromo-2-penten-l-yl)-2 -deoxyribosylfuranosyl thymidine (49), has been reported. The synthesis of this phosphoramidite was stereoselective and involved a Sakurai reaction between 5 -C-thymidine aldehyde and allyltrimethylsilane. Seela has reported the synthesis of the ribosyl-phosphoramidite derivatives of 7-bromo- and 7-iodo-8-aza-7-deazapurine-2,6-diamine (50a,b) from advanced synthetic precursors and of the bromo- and iodo-derivatives at the 5-position of uracyl phosphoramidite (51a,b). He further described the effect on base-pair stability due to their incorporation into oligonucleotide duplexes. ... 

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