Unusual triethylamine catalyzed rearrangement of bicyclic endoperoxides derived from substituted cycloheptatrienes

An Improved Synthesis of Cyclopropanes from Stabilized Phosphonates and 1,2-Dioxines

“…Of particular interest was the moderate to high yields of the Weinreb cyclopropanes 10a and 10b , derived from phosphonate 6d , and to our knowledge the first reported direct generation of Weinreb protected cyclopropanes without functional group manipulation. As previously reported with the methyl-keto ylide, the methyl-keto phosphonate 6e gave no cyclopropane with either 1a or 1b , as did phosphonate 6f, due to a competitive Kornblum−De La Mare rearrangement to afford 1,4-diketone. , α-Methyl-substituted phosphonate 6g gave moderate yields of the desired cyclopropanes as a mixture of diastereomers 11a and 11b (entry 16). In an attempt to increase the yield of cyclopropanes 11a and 11b , a different base, KHMDS, was tried, but it proved unsuccessful.…”

Rearrangements of organic peroxides and related processes

“…The treatment of endoperoxide 238 with Et 3 N gave 1,4-diketone 240 in quantitative yield instead of expected hydroxy ketone 239 ( Scheme 73 ) [ 350 – 352 ].…”

“…A further study [ 352 ] on the base-catalyzed rearrangements of substituted bicyclic endoperoxides showed that the pathway of the rearrangement is largely determined by the position of the substituent. The rearrangement of endoperoxides 247a , b containing an electron-withdrawing substituent in the seven-membered ring occurs mainly via a retro-aldol cleavage giving rise to formyl benzoates 248a , b ( Scheme 76 ).…”

Synthesis of naturally occurring tropones and tropolones

“…17-2A/B , Scheme 17). 109–112 Some of them could be converted to tropones via Kornblum-DeLaMare rearrangement 113 followed by elimination. 114 This was applied to the synthesis of stipitatic acid isomers as discussed in later sections.…”