Naphthalene proton sponges as hydride donors: diverse appearances of the tert-amino-effect

Abstract

It has been shown that the 1-NMe(2) group in the 2-substituted 1,8-bis(dimethylamino)naphthalenes (proton sponges) can intramolecularly donate a hydride ion to an appropriate electron-accepting ortho-substituent such as diarylcarbenium ion, β,β'-dicyanovinyl or methyleneiminium group. This produces the 1-N(+)(Me)=CH(2) functionality and triggers a number of further transformations (tert-amino effect) including peri-cyclization, ortho-cyclization or hydrolytic demethylation. In each particular case, the course of the reaction is determined by the nature of the ortho-substituent and the most potent nucleophile presenting in the reaction mixture. For 2,7-disubstituted 1,8-bis(dimethylamino)naphthalenes, two types of tandem tert-amino effect with the involvement of both peri-NMe(2) groups have been registered. The conclusion was made that proton sponges are generally more active in the tert-amino reactions than the corresponding monodimethylaminoarenes. This is ascribed both to higher electron donor ability of proton sponges and markedly shortened distance between electrophilic C(α)-atom in the ortho-substituent and hydrogen atoms of the nearest NMe(2) group. Most conversions observed proceed in good to high yields and are useful for the preparation of derivatives of benzo[h]quinoline, quino[7,8:7',8']quinoline, 2,3-dihydroperimidine, N,N,N'-trimethyl-1,8-diaminonaphthalene and proton sponge itself.

Study on the scope of tert‐amino effect: new extensions of type 2 reactions to bridged biaryls

“…To a solution of 2‐(pyrrolidin‐1‐yl)phenol (15.00 mmol, 2.45 g) in N , N ‐dimethylacetamide (15 mL), 2‐fluorobenzaldehyde (15.00 mmol, 1.58 mL) and K 2 CO 3 (30.00 mmol, 4.15 g) were added. The mixture was heated at 160 °C (oil temperature) under argon atmosphere for 1.5 h. To the cooled reaction mixture, EtOAc (20 mL) was added.…”

“…Further recent examples of type 2 tert ‐amino effect, including syntheses of pyrazolinoquinolizines and 1,4‐oxazinopyrazolines, 1,2‐fused 5 H ‐chromeno[4,3‐ b ]pyridin‐5‐ones and 6 H ‐benzo[ h ][1,6]naphthyridin‐5‐ones, naphthalenes, α‐carbolines, and spirocyclic 1,2,3,4‐tetrahydroquinolines, also demonstrate the versatility of such reactions.…”

Models for incomplete nucleophilic attack on a protonated carbonyl group and electron-deficient alkenes: salts and zwitterions from 1-dimethylamino-naphthalene-8-carbaldehyde

“…We observed this reaction earlier for zwitterion 6, 5 and Mátyus and co-workers 15,16 have reported similar reactions between ortho groups in the biphenyl series and between peri groups in the naphthalene series for which they have reported mechanistic evidence of intramolecular hydride transfer from deuterium labelling experiments. Pozharskii 19 has recently reported such reactions between ortho groups on naphthalene rings.…”

Heterocyclic superbases: retrospective and current trends

“…Both compounds 18 and 19 are less basic than diamine 11 by approximately half an order of magnitude. The reason for this is the chair-like geometry of the tetrahydropyridine rings which causes the hindrance for sufficiently strong IHB formation due to nonoptimal directional alignment of the lone electron pairs' axes of the nitrogen atoms [33]. This effect is especially clearly seen for 1,12-bis(dimethylamino)benzo[c]phenanthrene 20 [34].…”