Regioselective Synthesis of Substituted 4-Alkylamino and 4-Arylaminophthalazin-1(2H)-ones

Abstract

An efficient regioselective synthesis of substituted 4-alkylamino and 4-arylaminophthalazin-1(1H)-ones 5 is described. This new method features the formation of substituted phthalazin-1(1H)-ones 3 by the reaction of 2-formylbenzoic acids 1 or 3-hydroxyisobenzofuran-1(3H)-ones 2 with hydrazine to generate phthalazin-1(2H)-ones 3. Subsequent regioselective bromination of phthalazin-1(2H)-ones 3 with benzyltrimethylammonium tribromide (BTMA-Br3) followed by mixed copper-copper oxide-catalyzed amination of 4-bromophthalazin-1(2H)-ones 4 with primary amines generates aminophthalazin-1(2H)-ones in good overall yields.

Metal‐Free One‐Pot Tandem Construction of C4‐Phosphorylated Phthalazin‐1(2H)‐ones under Visible‐Light Photoredox Catalysis

“…C4‐Substituted phthalazin‐1(2 H )‐ones are essential constituents widely found in many biologically active products and pharmacologically valuable compounds, and the nature of the C4‐substituents play an important role in a broad spectrum of biological and pharmacological activities (Figure 1). [1] As a result, the efficient synthesis of these heterocycles has been the focus of much research effort for many years, [2,3] and diverse remarkable achievements have been accomplished in this field, including C4‐(hetero)arylation, [1h,3a–c,f–h,j,l,n–q,u,v] alkylation, [3b,d,e,k,l,u,v] amination, [1c,3c,i,m,s] alkenylation [3r] and sulfanylation [3t] of phthalazin‐1(2 H )‐ones. Recently considerable efforts have been made toward the efficient introduction of phosphorus moieties onto heterocycle rings because the presence of phosphorus moiety can tune the physical, chemical, and biological properties of the parent compounds, and many phosphorus‐substituted heterocycles can serve as ligands or organocatalysts in organic synthesis [4]…”

Visible‐Light Photoredox‐Catalyzed Tandem One‐Pot Construction of C4‐Difluoroalkylated Phthalazin‐1(2H)‐Ones

“…C4‐substituted phthalazin‐1(2 H )‐ones are key structural units ubiquitously found in a number of biologically active compounds displaying diverse pharmacological activities, [1] such as poly‐PARP inhibitor (Olaparib), [1d] histamine H1 receptor antagonist (Azelastine), [1e] aldose reductase inhibitor (Zopolrestat), [1f] Aurora kinase inhibitor, [1g] human A 3 adenosine receptor antagonist [1h] and proteasome inhibitor [1i] (Figure 1), and the nature of substituents present at the C4 positions have an important impact on their pharmacological activities. Accordingly, there has been a long‐standing research interest in the development of efficient methods for the synthesis of these heterocycles, [2,3] and impressive progress has been achieved in access to C4‐(hetero)arylated, [1i,3a–c,f–h,j,l,n–q,u,v] alkylated, [3b,d,e,k,l,u,v] aminated, [1g,3c,i,m,s] alkenylated [3r] and sulfanylated [3t] phthalazin‐1(2 H )‐ones. Recent years have witnessed ever‐growing research efforts within the synthetic community for incorporation of gem ‐difluoromethylene moiety into organic molecules because this group can effectively enhance the biological activities and the physicochemical properties of the parent compounds [4] .…”