Synthesis of spiro[2.5]octa-4,7-dien-6-one with consecutive quaternary centers via 1,6-conjugate addition induced dearomatization of para-quinone methides

Abstract

An efficient one-pot approach for the synthesis of spiro[2.5]octa-4,7-dien-6-ones by employing para-quinone methides has been developed. The reaction proceeded smoothly in high yields under mild conditions without the use of metals. Moreover, all products obtained herein contained two or three consecutive quaternary centers.

Polyfunctional Sterically Hindered Catechols with Additional Phenolic Group and Their Triphenylantimony(V) Catecholates: Synthesis, Structure, and Redox Properties

“…The CV data for thioethers L1-L3 and triphenylantimony(V) catecholates 1 and 2 in CH2Cl2 (GC anode, С = 3•10 −3 М, Ar, 0.15 M Bu4NClO4, vs Ag/AgCl/KCl(sat.)). The oxygen-to-carbon bonds O(1)-C(1) and O(2)-C(2) (1.358(2) and 1.366(2) Å, respectively) are ordinary and typical for catecholato complexes of different metals [65], and bond O(3)-C(19) (1.376(2) Å) is the longest O-C bond in 1, which is typical for sterically hindered phenols [66][67][68]. The six-membered carbon ring C(1-6) is aromatic, with average C-C bond distances of 1.400 ± 0.015 Å, which is very close to the same value for catechol L 1 .…”

“…The oxygen-to-carbon bonds O(1)-C(1) and O(2)-C(2) (1.358(2) and 1.366(2) Å, respectively) are ordinary and typical for catecholato complexes of different metals [65], and bond O(3)-C(19) (1.376(2) Å) is the longest O-C bond in 1, which is typical for sterically hindered phenols [66][67][68]. The six- Figure 1.…”

1,6‐Addition Arylation of para‐Quinone Methides: An Approach to Unsymmetrical Triarylmethanes

“…Recently, para ‐quinone methides ( p ‐QMs), an important and readily available class of synthetic intermediates, have been used to construct diarylmethines through 1,6‐conjugate addition ,. [8c] In 2015, Anand's group reported a Pd‐catalyzed annulation of ortho ‐alkynylanilines followed by 1,6‐addition of p ‐QMs for the synthesis of unsymmetrical triarylmethanes bearing indole groups . Sun's group achieved the synthesis of unsymmetrical triarylmethanes containing pyrrole groups through the chiral‐phosphoric‐acid‐catalyzed 1,6‐conjugate addition of in‐situ‐generated p ‐QMs with 2‐methylpyrroles .…”

Phosphoric Acid Catalyzed Asymmetric 1,6‐Conjugate Addition of Thioacetic Acid topara‐Quinone Methides

“…To date,o nly very limited examples of enantioselective additions of p-QMs have been documented. [9,10] In 2013, Fanand co-workers realized acatalytic asymmetric 1,6conjugate addition of p-QMs with malonates under phasetransfer catalysis. [9a] Shortly afterwards,J ørgensen described anew organocatalytic concept for asymmetric a-alkylation of aldehydes by 1,6-conjugate addition of enamines to p-QMs.…”