Timesavings associated with microwave-assisted synthesis a quantitative approach

Timesavings associated with microwave-assisted synthesis a quantitative approach 

The use of microwave-assisted organic synthesis has been claimed in a number of publications to accelerate the production of novel chemical entities1-4. However, little effort has been put forth to quantitate these timesavings and most claims have few experimental controls. This chapter will focus on direct comparisons between microwave-assisted synthesis and traditional thermal heating. The primary objective is to discuss the examples our group has presented, which contain direct comparisons, and to highlight controlled direct comparisons from the literature5-8. The secondary objective is to focus on overall productivity increases associated with microwave-assisted synthesis. 

Our final objective is to show new developments in microwave-technology hardware, specifically to illustrate examples of chemistry and new tools, such as plate-based systems, for improving the throughput of microwave-assisted library production. 

Timesavings associated with microwave-assisted synthesis 

At this time, we had access to a microwave system from Personal Chemistry called the Smith Synthesizer (Personal Chemistry AB, Uppsala, Sweden) and so we attempted this difficult cycloaddition reaction13. As evident in Table 8.1, the results with the microwave were remarkably improved compared to the conventionally heated counterpart. The product yield and purity was substantially higher than what was observed in the pressure tubes. With this first positive example, we were encouraged to try systems that had not been able to produce an observable product in the pressure tubes. The condensation of a fused cyclohexyl maleimide had not produced any product in our previous efforts, but with microwave heating for a short 5 min reaction time at 180°C we were able to isolate a satisfactory amount of the desired product. 

---

Timesavings associated with microwave-assisted synthesis A quantitative approach", C. R. Sarko in Microwave Assisted Organic Synthesis edited by J. P. Tierney and P. Lidstrom, Blackwell Publishing, Oxford, 2005. 

---