Polyurethanes (PUs) are synthetic substances that satisfy the requirements of many industrial applications, such as films, foams, coatings, adhesives, biomedical devices, sealants, composite materials, and elastomers. The polyaddition reaction of isocyanates, categorized as CMR (carcinogenic, mutagenic, and reprotoxic), and polyols produces commercial PUs. As a result of numerous concerns about the toxic and hazardous properties of isocyanates, which limit their utilization, researchers are being encouraged to develop alternative processes for producing PUs. Nonisocyanate polyurethanes (NIPUs) are synthesized using a sustainable and eco-friendly approach to replace the toxic, hazardous, and detrimental characteristics of isocyanates. Among NIPU’s synthesis methods, aminolysis of cyclic carbonates (CCs), transurethanization, ring-opening polymerization (ROP), and rearrangement are included, with aminolysis of CCs emerging as a potential approach. Novel approaches to obtain materials with improved performance, such as functional groups like acrylates, methacrylates, POSS, and epoxies, may be necessary. Consequently, different approaches for hybrid polyhydroxyurethanes (PHUs) and distinct prepolymerization techniques for NIPUs are delineated. This review work is divided into two sections. The initial section focuses entirely on isocyanate-based methodologies for producing commercial PUs, while the subsequent section is exclusively dedicated to synthesizing NIPUs. This review encompasses all methods employed to produce commercial PUs, NIPUs, and H-NIPUs.
