Fluoride‐Catalyzed Deblocking: A Route to Polymeric Urethanes

• Published in: Angewandte Chemie International Edition Vol. 57; no. 17; pp. 4599 - 4602
• Main Authors: Sheri, Madhu, Choudhary, Umesh, Grandhee, Sunitha, Emrick, Todd
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 16.04.2018; Wiley Subscription Services, Inc
• Edition: International ed. in English
• Subjects: blocking; Carbamate compounds; Chemistry; Chemistry, Multidisciplinary; cross-linked polyurethane; Diols; Fluorescence; fluoride-catalyzed deblocking; Fluorides; High temperature; Isocyanates; Organometallic compounds; Physical Sciences; Polymerization; Polyurethane; Polyurethane resins; Science & Technology; Urethanes; ION DETECTION; fluoride-catalyzed deblocking; POTASSIUM FLUORIDE; cross-linked polyurethane; fluorescence; N-CHLOROBENZAMIDE; blocking; BLOCKED ISOCYANATES-III; CHEMISTRY; COATINGS; SUPRAMOLECULAR POLYMER; polyurethane; CYCLIZATION
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201800795

We report a fluoride‐catalyzed deblocking of urethanes as “blocked” isocyanates. Organic and inorganic sources of fluoride ion proved effective for deblocking urethanes and for converting polyurethanes to small molecules. Distinct from conventional deblocking chemistry involving organometallic compounds and high temperatures, the method we describe is metal‐free and operates at or slightly above room temperature. The use of fluorescent blocking agents enabled visual and spectroscopic monitoring of blocking/deblocking reactions, and the selected conditions proved applicable to urethanes containing a variety of blocking groups. The method additionally enabled a one pot deblocking and polymerization with α,ω‐diols. Overall, this deblocking/polymerization strategy offers a convenient and efficient solution to problems that have limited the breadth of applications of polyurethane chemistry. Releasing blockages: A new method of urethane deblocking and polyurethane formation using fluoride ion as an efficient catalyst is reported. Fluorescent blocking groups enable easy visual and spectroscopic monitoring of blocking/deblocking reactions, and it is anticipated that this method will offer an efficient solution to problems that have limited the breadth of applications of polyurethane chemistry.