Carbocationic synthons Synthon

fig. 1: strategic disconnection en route hops ether



fig 2: pictet-spengler disconnection.

many retrosynthetic disconnections important organic synthesis planning use carbocationic synthons. carbon-carbon bonds, example, exist ubiquitously in organic molecules, , disconnected during retrosynthetic analysis yield carbocationic , carbanionic synthons. carbon-heteroatom bonds, such found in alkyl halides, alcohols, , amides, can traced backwards retrosynthetically polar c-x bond disconnections yielding carbocation on carbon. oxonium , acylium ions carbocationic synthons carbonyl compounds such ketones, aldehydes , carboxylic acid derivatives. oxonium-type synthon used in disconnection en route hops ether, key component of beer (see fig.1). in forward direction, researchers used intramolecular aldol reaction catalyzed titanium tetrachloride form tetrahydrofuran ring of hops ether.

another common disconnection features carbocationic synthons pictet-spengler reaction. mechanism of reaction involves c-c pi-bond attack onto iminium ion, formed in situ condensation of amine , aldehyde. pictet-spengler reaction has been used extensively synthesis of numerous indole , isoquinoline alkaloids.

carbanion alkylation common strategy used create carbon-carbon bonds. alkylating agent alkyl halide or equivalent compound leaving group on carbon. allyl halides particularly attractive sn2-type reactions due increased reactivity added allyl system. celestolide (4-acetyl-6-t-butyl-1,1-dimethylindane, component of musk perfume) can synthesized using benzyl anion alkylation 3-chloro-2-methyl-1-propene intermediate step. synthesis straightforward, , has been adapted teaching purposes in undergraduate laboratory.