The “Fully Catalytic System” in Mitsunobu Reaction Has Not Been Realized Yet

Abstract

An investigation of the recently reported "fully catalytic Mitsunobu reaction" using catalytic amounts of a phosphine reagent and an azo reagent has shown that although benzyl 4-nitrobenzoate is formed under the fully catalytic conditions, the same result is obtained if the hydrazine catalyst is omitted, indicating that this is not a Mitsunobu reaction. In addition, when the reaction between (-)-ethyl lactate and 4-nitrobenzoic acid was carried out using the "fully catalytic" method, the corresponding ester was formed but in very low yield and with predominant retention of configuration. Unfortunately, the system catalytic in phosphine reagent is incompatible with that in the azo reagent.

Cross‐Linked Surface Engineering to Improve Iron Porphyrin Catalytic Activity

“…[ 44 ] As a number of prior reports have already described the preparation of aromatic azo compounds using iron (II) phthalocyanine (Fe(Pc)) as the catalyst. [ 45–49 ] To our knowledge, Fe(Pc) as catalyst has great potential as oxidation catalysts, however, the Fe(Pc) molecule cannot be recycled, resulting in a significant waste and environmental pollution. Against this backdrop, we particularly focus on the cross‐linked surface engineering with respect to the hollow skeleton for the rational design of heterogeneous catalysts in terms of functionalization methods and structure correlated catalysis.…”

Strategy for the Use of Molecular Oxygen in Organic Synthesis

“…32 After that report, however, we demonstrated that their 'fully' catalytic Mitsunobu reaction did not work because inversion of stereochemistry was not observed in an ester product obtained (in low yield) from the reaction of a chiral secondary alcohol. 33,34 Very recently, Denton's group reported azo reagent-free and redox-neutral catalytic Mitsunobu reactions using an originally designed phosphine oxide catalyst. 35 This reaction involves a dehydration process to activate the catalyst by strong acids, but inversion of stereochemistry fully occurs by the formation of alkoxy phosphonium intermediates from the activated catalyst and secondary alcohols.…”

The catalytic Mitsunobu reaction: a critical analysis of the current state-of-the-art

“…This tantalizing possibility was investigated by Taniguchi, Košmrlj and co-workers 30 in which the mechanism of the double catalytic system was probed. The study began by revisiting the esterification of benzyl alcohol (Scheme 13a).…”