Synthesis of Primary gem-Dihydroperoxides and Their Peroxycarbenium [3 + 2] Cycloaddition Reactions with Alkenes

It is long known that dihydroperoxidation of aliphatic aldehydes is extremely difficult and normally stops halfway at the hydroxyhydroperoxide stage. This strange phenomenon now has been explored, and a highly effective protocol for conversion of aliphatic aldehydes into gem-dihydroperoxides has been developed. Silyl protection of primary gem-dihydroperoxides, which is also a challenge due to unexpected based-induced decomposition, was achieved using 2,6-lutidine as the base. The silyl-protected gem-dihydroperoxides were then examined in a peroxycarbenium [3 + 2] cycloaddition reaction with alkenes for the first time. Aromatic substrates normally reacted smoothly, affording the expected 1,2-dioxolanes smoothly. Aliphatic aldehydes generally failed to yield 1,2-dioxolane. In all cases, unexpected formation of either a chlorohydrin or a 1,2-dichloride (with Cl atoms derived from TiCl₄) depending on the alkene employed was observed, which displays some so far unknown facets of the cycloaddition and helped to gain many mechanistic insights.