Domino cyclization alcoholic groups

Anionic domino processes are the most often encountered domino reactions in the chemical literature. The well-known Robinson annulation, double Michael reaction, Pictet-Spengler cyclization, reductive amination, etc., all fall into this category. The primary step in this process is the attack of either an anion (e. g., a carban-ion, an enolate, or an alkoxide) or a pseudo anion as an uncharged nucleophile (e. g., an amine, or an alcohol) onto an electrophilic center. A bond formation takes place with the creation of a new real or pseudo-anionic functionality, which can undergo further transformations. The sequence can then be terminated either by the addition of a proton or by the elimination of an X group. 

There are also some rare domino sequences where two anionic and two radical reactions are combined (Scheme 2.152) [347]. According to a report of the Wang group, thionyl chloride is able to promote a succession of reactions by an initial formation of a chlorosulfite 2-673 of the tertiary alcohol 2-672, followed by an SN-type reaction to produce the chloroallene 2-674. A Schmittel cyclization reaction [348] then generates... 

A similar concept was applied to the two-component synthesis of indoles 164 via cydoisomerization of alkynyl imines 162 (Scheme 9.61) [220]. N-(Alkoxymethyl) indoles 164 were readily prepared through the Cu(I)-catalyzed cyclization-hydroxyla-tion reaction of the imine precursors 162 in the presence of a variety of external O-nucleophiles 163, such as alcohols and phenols, with good functional group compatibility. The authors believe that this domino reaction begins with the Cu( I)-activation of alkyne 162 toward 5-ewdo-digcyclization to form a cydic metal-containing azomethine... 

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