Pyrrolidino-functionalised 1,8-bis(dialkylamino)naphthalenes undergo mild peri-quaternisation, either intra- or intermolecularly, resulting in both stable quaternary salts with peri-situated dialkylamino and trialkylammonium groups and their reactive transient variants. For the first time,...
The reaction of 1-dimethylamino-8-(methylamino)naphthalene with 1,3-dibromopropane chemoselectively leads to the product of N,N′-heterocyclization, while in the case of 1,4-dibromobutane and 1,2-bis(bromomethyl)benzene the process results in heterocyclization onto the same nitrogen atom with the formation of previously unknown 1-dimethylamino-8-pyrrolidino- and 1-dimethylamino-8-isoindolino-naphthalenes. The same reactions conducted without adding any auxiliary base lead to the formation of N,N′-linked double proton sponges as a new type of polynitrogen organic receptor. Proceeding as a sequence of quaternization–demethylation–cyclization steps, this heterocyclization process can also be used to construct six-membered rings (piperidino, morpholino), albeit in lower yields. The ability of 1,2-dibromoethane to brominate N-alkylated 1,8-diaminonaphthalenes is also described. It is shown for the first time that a commercially available 1,8-bis(dimethylamino)naphthalene (DMAN) can be used as a starting material in a heterocyclization reaction, which via a one-pot approach and in a short time can be converted into 1,5-dimethylnaphtho[1,8-bc]-1,5-diazacyclooctane or 1-dimethylamino-8-(pyrrolidin-1-yl)naphthalene.
The interaction of 1,8‐diaminonaphthalene with o‐xylylene dibromide leads to two topologically relevant isomeric products, 1,8‐di(isoindolin‐2‐yl)naphthalene (reported previously), and its structural isomer with the bridgehead nitrogens in a bicyclic system (reported for the first time). This is the first case of isolating two heterocyclic analogs of 1,8‐bis(dimethylamino)naphthalene (proton sponge or DMAN) in one reaction. Both isomers are formed in parallel reactions and are not interconverted upon acid treatment. The first representative of heterocyclic “amide proton sponges”, which is still able to participate in intramolecular protonation due to the amide nitrogen atom, was synthesized by direct oxidation of the corresponding isoindoline derivative. Using p‐xylylene dibromide as a bridging bielectrophile, a macroheterocyclization was effectively realized to construct the first paracyclophane extended by two DMAN subunits. Mostly driven by the proximity effect, the molecular structure, unusual protonation trends and reactivity of peri‐diaminonaphthalenes N‐linked with o‐ and p‐xylylene fragments are also discussed.
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