In our initial attempts of the reaction between α-bromoacetophenone 1a and α-(methylthio)styrene 2a, using a variant of the ERED from Gluconobacter oxydans (GluER T36A), we were pleased to observe the formation of predominantly a single product by HPLC (Table , entry 1; Figure ); however, this product appeared more hydrophilic than expected. Analysing the reaction further by GC-MS, we observed two products that were identified as α-(methylthio)acetophenone 6a and a second product with a mass and fragments consistent with 7a (Figure ). Expecting a competing dehalogenation of substrate 1a to give acetophenone 4a, we had used an excess of 1a. We speculated that product 3aa was indeed formed (Scheme 1), but sufficiently nucleophilic to react with a second equivalent of substrate 1a, forming sulfonium 5aa (observed by HPLC). Upon heating during GC-MS injection, 5aa eliminates 6a thus forming the two observed products. Indeed, incubating isolated 3aa with 1a under reaction conditions (no ERED), we observed the formation of the same products (Figure ). Reducing the equivalents of 1a (Table , entries 2-4; Figure ,43), the undesired product peak(s) decreased and the desired product 3aa was the predominant product formed. Using equal amounts of 1a and 2a proved to give the highest conversions to product 3aa. We also explored analogues of 1a bearing weaker leaving groups, namely αchloroacetophenone (Cl-1a) and α-fluoroacetophenone (F-1a), and while indeed the undesired product was no-longer observed (Figure ), the formation of 3aa was also diminished or fully abolished, respectively (Table , entries 5-6). Next, we explored the catalyst loading and found that decreasing the catalyst loading resulted in both lower conversion and ee, while increasing the loading increased both slightly (Table , entries 8-9, Figure ). Doubling the substrate concentration, we observed comparable conversion and enantioselectivity (Table , entry 10, Figure ). Again, using a lower catalyst loading reduced both conversion and ee, albeit to a lesser extent than at the lower substrate concentration (Table , entry 11, Figure ). Curious as to the reduced ee, we carried out a time course of the reaction and observed small amounts of putative 5aa formed transiently (Figure ; Figure ). We were curious whether the reaction shown in Scheme 1 was reversible, leading to racemization of 3aa over time; however, we observed no loss in ee when incubating isolated 3aa with 1a (Figure ). Thus, we are currently unable to explain the reduction in ee for slower reactions. Having identified suitable reaction conditions with GluER T36A, we looked at a small panel of EREDs. Both NCR from Zymomonas mobiles and PETNR from Enterobacter cloacae showed conversion to the desired product, while OYE3 from Saccharomyces cerevisiae showed no product formation (Table , entries 13-15, Figure ). Like GluER T36A, NCR selectively formed the (R)-enantiomer but with lower conversions and ee, while PETNR forms the opposite (S)-enantiomer albeit with lower ee. Control reactions with FMN, or with GluER T36A in the presence of oxygen, showed no conversion, with the latter showing a variety of unidentified side products (Table , entries 7&12, Figure ).