The development of novel reaction modes enables the discovery of new reaction mechanism and unknown skeletons [
7,
8]. Enaminones are emerging synthetic building blocks capable of providing multiple nucleophilic or electrophilic reaction sites and thus have the potential to allow new reactions modes. In recent years, numerous elegant research works have been reported by Wan and Yu
et al., and the multiple reactivity of enaminone has been deeply investigated [
9–
17]. Specifically, the currently reported mono-functionalisation reactions of enaminones were mainly focused on the regionally selective modification of the
α- or
β-positions of C═C with heteroatoms to construct C—X bonds (
Scheme 1a) [
18–
23]. As shown in this scheme, there are numerous reaction modes available for the bi-functionalization of enaminones. (a) Using “CO” and
β-positions as triatomic synthons for the construction of five- or six-membered rings [
24–
31]. (b) On the basis of the cleavage of a C—N bond at the
β-position, the
β,β-disubstituted phenylacetones or 2-substituted chromones can also be obtained [
32–
36]. (c) The different activities of
α- and
β-positions can be used to achieve the installation of bifunctional groups [
37,
38], the construction of heterocycles by [2 + n] cyclization reactions [
39–
46], and abundant use of
o-hydroxyphenyl enaminones to construct 3-substituted chromone skeletons (
Scheme 1b) [
47–
53]. In contrast, tri-functionalization reactions of enaminones are rarely and only a few examples have been reported. Among these, works involving the “CO”,
α- and
β-positions have allowed the synthesis of trisubstituted pyrazoles and pyrrolo[3,4-
c]quinolineones. Recently, our group achieved the construction of chromeno[2,3-
b]pyrrolones skeleton using
o-hydroxyphenyl enaminones
via multiple cyclization reactions at the
α-,
β- and
β-positions (
Scheme 1c) [
54–
57]. However, the higher order functionalization reaction mode of enaminones has been undiscovered even to date. Here, we exhaustively used the four reaction sites, “CO”,
α-,
β-, and
β-positions, to successfully achieve the tetra-functionalization reaction of enaminones, resulting the discovery of the unknown furo[2′,3′:4,5]pyrimido[1,2-
b]indazole skeleton. Furthermore, this efficiently assembled synthetic method provided a new strategy for the design of luminescent materials for the obtained polycyclic heterocyclic skeleton showed typical AIE feature (
Scheme 1d).