TY - JOUR AU - Smyth, Megan; Moody, Thomas S.; Wharry, Scott; Baumann, Marcus TI - Continuous-Flow Synthesis of Cyclobutenes Using LED Technology SN - 0936-5214 SN - 1437-2096 PY - 2023 JO - Synlett JF - Synlett LA - EN VL - 35 IS - 03 SP - 285 EP - 290 DA - 2023/06/06 ET - 2023/05/04 KW - photochemistry KW - cycloaddition KW - cyclobutene KW - light-emitting diode (LED) KW - flow chemistry AB - Cyclobutenes are highly strained ring systems of considerable synthetic interest that can be accessed via cycloaddition reactions between alkenes and alkynes. However, their traditional preparation relies on photochemical [2+2] cycloadditions that exploit low-wavelength UV radiation emitted from inefficient medium-pressure Hg lamps. This paper reports on the development of a modern approach using a high-power LED set-up emitting at the boundary of UV-A and visible light in conjunction with a continuous-flow reactor. The resulting flow process renders a series of cyclobutenes from maleimides and various commercial alkynes. This provides a more energy-efficient approach that is readily scalable to access multigram quantities of cyclobutenes in high chemical yields and short residence times. The value of these products is exemplified by flow-based hydrogenations yielding highly substituted cyclobutanes which represent sought after building blocks in modern medicinal chemistry programs. PB - Georg Thieme Verlag KG DO - 10.1055/a-2086-0630 UR - http://www.thieme-connect.de/products/ejournals/abstract/10.1055/a-2086-0630 ER -