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2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (or DDQ) is the chemical reagent with formula C 6 Cl 2 (CN) 2 O 2. This oxidant is useful for the dehydrogenation of alcohols, [3] phenols, [4] and steroid ketones. [5] DDQ decomposes in water, but is stable in aqueous mineral acid. [6]
(1) Fmoc-protected amino group, (2) benzyl ester protected carboxyl group and (3) tert-butyl ether protected phenolic hydroxyl group of Tyrosine. Orthogonal protection is a strategy allowing the specific deprotection of one protective group in a multiply-protected structure.
Typically, selective cleavage of a PMB ether in the presence of a benzyl ether uses strong stoichiometric oxidants such as 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) or ceric ammonium nitrate (CAN). PMB ethers are far more susceptible to oxidation than benzyl ethers since they are more electron-rich.
2,3-Dichloro-5,6-dicyano-p-benzoquinone (DDQ) [18] Conditions for deprotection of benzyl group are applicable for cleavage of the PMB protecting group Amine protection
Completing the cyclooctane ring required 3 more carbon atoms that were supplied by a C2 fragment in an aldol addition and a Grignard C1 fragment (scheme 2).A Mukaiyama aldol addition (magnesium bromide / toluene) took place between aldehyde 7 and ketene silyl acetal 8 with 71% stereoselectivity to alcohol 9 which was protected as the TBS ether 10 (TBSOTf, 2,6-lutidine).
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Depending on pH, solvent and the extent of substitution, the aci-nitro intermediate decays at a rate of roughly 10 2 –10 4 s −1. [2] Following resonance of the π-electrons, a five-membered ring is formed before the PPG is cleaved yielding 2-nitrosobenzaldehyde and a carboxylic acid. Overall, nitrobenzyl-based PPGs are highly general.
Colton Sissons and Filip Forsberg each scored to give the Predators a 2–1 lead after the first period. Then Steven Stamkos and Fedor Svechkov added goals in the first two minutes of the second ...