Intramolecular 1,5- versus 1,6-hydrogen abstraction reaction promoted by alkoxyl radicals in pyranose and furanose models

TLDR: In this paper, the primary alkoxyl radical generated by reaction of 1-(2-hydroxyethyl)-glycosides with DIB and iodine can undergo regioselective intramolecular hydrogen abstraction (IHA) reactions to furnish four different dioxabicyclic systems derived from carbohydrates.

About: This article is published in Tetrahedron.The article was published on 2007-09-03 and is currently open access. It has received 23 citations till now. The article focuses on the topics: Hydrogen atom abstraction & Furanose.

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Table 1. IHA reaction of 3,7-anhydrooctitols and 3,6-anhydroheptitolsa

Frequently asked questions

Q1. What are the contributions in "Intramolecular 1,5- versus 1,6-hydrogen abstraction reaction promoted by alkoxyl radicals in pyranose and furanose models" ?

In this paper, the primary alkoxyl radical generated by reaction of 1- ( 2-hydroxyethyl ) -glycosides with DIB and iodine can undergo regioselective intramolecular hydrogen abstraction ( IHA ) reactions to furnish four different dioxabicyclic systems derived from carbohydrates. 

Q2. How many mmol of phosphorous pentoxide was added to the mixture?

To a solu- tion of compound 19 (1.9 g, 9.4 mmol) in dry CHCl3 (55 mL) was added an excess of dimethoxymethane (55 mL, 632.5 mmol), phosphorous pentoxide (28 g, 197 mmol) and stirred at room temperature under nitrogen atmosphere for 3 h. 

Q3. how much c12h22o4 is a colourless oil?

Purification of the residue by column chromatography (CHCl3–MeOH, 9:1) gave compound 19 (81.5 mg, 0.40 mmol, 90%) as a colourless oil: [a]D —2.3 (c, 2.05); IR (CCl4) 3360, 2931, 1732, 1652, 1442, 1285, 1108, 1040 cm—1; 1H NMR 2.52 (1H, dd, J¼8.4, 15.4 Hz), 2.67 (1H, dd, J¼4.3, 15.5 Hz), 3.54 (1H, dd, J¼4.5, 12.0 Hz), 3.63 (1H, dd, J¼3.6, 12.0 Hz), 3.67 (3H, s), 3.76 (1H, dd, J¼6.0, 6.0 Hz), 4.80 (1H, ddd, J¼4.4, 4.4, 8.1 Hz), 3.95 13 (1H, dd, J¼4.4, 5.6 Hz), 4.09 (1H, m), 4.83 (3H, br s); C NMR 37.7 (CH2), 50.7 (CH3), 61.9 (CH2), 71.0 (CH), 74.4 (CH), 78.8 (CH), 84.8 (CH), 172.0 (C); MS (EI) m/z (rel intensity) (FAB) 229 (M++Na, 100), 207 (M++H, 100). 

Q4. What is the entropic penalty of the radicals?

HAT reaction through eight-membered transition states orhigher promoted by alkoxyl radicals which suffer a severe entropic penalty are practically unknown. 

Q5. what is the reaction of a tetrahydrooctitol?

A solution of 3,7- anhydroocti- tols or 3,6-anhydroheptitols (1 mmol) in dry CH2Cl2 (25 mL) containing (diacetoxyiodo)benzene (DIB) and iodine (1 mmol) was irradiated with two 80 W tungsten filament lamps at room temperature under nitrogen until the reaction was completed. 

Q6. How many ml of allyltrimethylsilane were added to a?

To a solution of com- pound 1420 (6.2 g, 18.6 mmol) in dry MeCN (60 mL) were added allyltrimethylsilane (9.3 mL, 58.5 mmol) and BF3$OEt2 (6.2 mL, 48.9 mmol) at 0 ○C. 

Q7. what is the chemistry of a hexanes?

Column chromatography (hexanes–EtOAc, 7:3) of the residue afforded compound 24 (1.98 g, 5.24 mmol, 92%) as a colourless oil: [a]D +18 (c, 0.5, EtOAc); 1H NMR 1.33 (3H, s), 1.37 (3H, s), 1.44(3H, s), 1.50 (3H, s), 1.73 (2H, ddd, J¼6.2, 6.4, 8.1 Hz), 3.55 (2H, dd, J¼6.5, 6.5 Hz), 3.72 (1H, dd, J¼3.7, 7.7 Hz), 4.01 (1H, dd, J¼4.5, 8.7 Hz), 4.09 (1H, dd, J¼6.4, 8.7 Hz), 4.24 (1H, dd, J¼7.4, 7.4 Hz), 4.39 (1H, ddd, J¼4.4, 6.2, 7.7 Hz), 4.50 (2H, s), 4.59 (1H, dd, J¼0.8, 6.1 Hz), 4.75 (1H, dd, J¼3.8, 6.2 Hz), 7.27–7.38 (5H, m); 13C NMR 25.1 (CH3), 25.6 (CH3), 26.5 (CH3), 27.3 (CH3), 67.2 (CH2), 67.4 (CH2), 73.5 (CH2), 73.9 (CH), 80.6 (CH), 81.1 (CH), 82.0 (CH), 85.9 (CH), 109.5 (C), 112.9 (C), 127.9 (3×CH), 128.7 (2×CH), 138.7 (C); MS (FAB+) m/z (rel intensity) 401 (M++Na, 1), 379 (M++H, 4), 363 (6); HRMS calcd for C21H31O6 379.2121, found 379.2117. 

Q8. What is the chemistry of a cyclic ether?

Bicyclic ketals can be easily converted into the correspondingbicyclic ethers by stereoselective reduction: (a) Takemoto, Y.;Furuse, S.-I.; Hayase, H.; Echigo, T.; Iwata, C.; Tanaka, T.; Ibuka, T. Chem.