The use of renewable feedstock is one of the twelve key principles of sustainable chemistry. Unfortunately, bio-based compounds often suffer from high production cost and low performance. To fully tap the potential of natural compounds it is important to utilize their functionalities that could make them superior compared to fossil-based resources. Here we show the conversion of (+)-3-carene, a by-product of the cellulose industry into ε-lactams from which polyamides. The lactams are selectively prepared in two diastereomeric configurations, leading to semi-crystalline or amorphous, transparent polymers that can compete with the thermal properties of commercial high-performance polyamides. Copolyamides with caprolactam and laurolactam exhibit an increased glass transition and amorphicity compared to the homopolyamides, potentially broadening the scope of standard polyamides. A fourstep one-vessel monomer synthesis, applying chemo-enzymatic catalysis for the initial oxidation step, is established. The great potential of the polyamides is outlined.

The synthesis and polymerization of two β‐lactams and two ε‐lactams derived from the terpenes α‐pinene and (+)‐3‐carene are reported. The new biopolymers can be considered as polyamide 2 (PA2) and polyamide 6 (PA6)‐types with aliphatic stereoregular side chains, which lead to remarkable new properties. The macromolecules are investigated by gel permeation chromatography (GPC), nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and infrared (IR). The (+)‐3‐carene‐derived PA6‐type is of particular interest, since it reaches a molecular weight of over 30 kDa, which is the highest value for lactam‐based polyamides derived from terpenes reported to date. Additionally, a glass transition temperature (Tg) of 120 °C is observed, surpassing the glass transition temperature of PA6 by 60 °C. The absence of a melting point (Tm) indicates high amorphicity, another novelty for terpene‐based polyamides, which might give transparent bio‐polyamides access to new fields of application.

Back Cover: (+)‐3‐Carene and α‐pinene are abundant monoterpenes from wood and valuable biogenic resources for substituted lactams. These lactams can be used for the production of new bio‐polyamides with surprising and promising properties. In article number 1800903, Volker Sieber and co‐workers observe a high‐performance glass transition temperature, high degree of amorphicity, molecular weights in the range of industrial polyamides, and a reduced water uptake for the (+)‐3‐carenebased polyamide.

In this work, the synthesis of limonene lactam starting from limonene epoxide and its subsequent ring-opening polymerization (ROP) to novel polyamides is presented. Sustainable, biobased materials are gaining interest as replacements of conventional, petroleum-based materials, and even more important, as high-performance materials for new applications. Terpenes-structurally advanced biobased compounds-are therefore of great interest. In this research, limonene lactam, a novel biobased monomer for preparing sustainable polyamides via ROP, can be synthesized. Limonene lactam possesses an isopropylene and a methyl side group, thus stereocenters posing special challenges and requirements for synthesis, analysis and polymerization. However, these difficult-to-synthesize structural elements can generate novel polymers with unique properties, e.g., functionalizability. In this work, a sustainable monomer synthesis is established, and simplified to industrial needs. For the sterically demanding in-bulk ROP to limonene polyamides, various initiators and conditions are tested. Polyamides with more than 100 monomer units are successfully synthesized and confirmed via nuclear magnetic resonance (NMR) spectroscopy and gel permeations chromatography (GPC). Differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) are used to analyze its thermal properties. In summary, a sustainable monomer synthesis is established, and promising polyamides with intact double bond and interesting thermal properties are achieved.

(Pivaloyloxymethyl)zinc chloride, obtained by an iodine-magnesium exchange and subsequent transmetalation, shows a much higher reactivity in Negishi cross-couplings than the corresponding zinc organometallic, prepared by direct zinc insertion. Furthermore, a substituted derivative of (pivaloyloxymethyl)zinc chloride is prepared starting from pivaloyloxymethyl sulfoxide using TMPZnCl•LiCl (TMP = 2,2,6,6-tetramethylpiperidyl), followed by a sulfoxide-magnesium exchange.