RESUMEN
From the variety of methods known for the depolymerization of organosolv lignin, a broad range of diversely substituted aromatic compounds are available today. In the present work, a novel two-step reaction sequence is reported, which is focused on the formation of phenols. While the first step of the depolymerization strategy comprises the 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)-catalyzed oxidation of organosolv lignin with nitrogen monoxide so that two waste materials are combined, cleavage to the phenolic target compounds is achieved in the second step employing hydrazine and potassium hydroxide under Wolff-Kishner-type conditions. Besides the fact that the novel strategy proceeds via an untypical form of oxidized organosolv lignin, the two-step sequence is further able to provide phenols as cleavage products, which bear no substituent at the 4-position.
RESUMEN
In this work, a novel phenethylamine-derived protecting group is introduced, which is able to significantly enhance the Grubbs I-catalyzed formation of 9- to 12-membered lactams through charge-induced conformational fixation under acidic conditions. As the new approach is particularly valuable for 10- and 11-membered ring systems, for which no related precedence was available so far, the overall strategy now offers general access to medium-sized lactams via ring closing metathesis. Cleavage of the protecting group can be achieved through a mild sequence combining N-oxidation and Cope elimination or alternatively under standard hydrogenation conditions.
RESUMEN
The radical 5-exo cyclization starting from 2-allyloxyphenyldiazonium ions can be employed for the diastereoselective synthesis of ortho-spirocyclohexadienones through a consecutive addition to alkynes. The spirocyclic systems are formed in a radical [2 + 2 + 1] cycloaddition comprising three carbon-carbon formations, of which the final one is an ipso attack onto the aromatic system at the original position of the diazonium-derived aryl radical.