One-Pot Preparation of Ethyl 2(Z)-4-(Anilinoxy)pentenoate by α-Aminoxylation of Propanal Followed by Z-Selective HWE Reaction and the Study on Its Cyclization Reaction

One-Pot O2-Oxidation and the Horner–Wadsworth–Emmons Reaction of Primary Alcohols for the Synthesis of (Z)-α,β-Unsaturated Esters

“…The reaction of benzyl alcohol 2m was completed in 3 h, and 3m was obtained in 94% yield with Z / E = 92:8 using K 3 PO 4 in MeCN (entry 12). In general, the selectivity of our Z -selective HWE reaction is the highest when a Na base is used for aliphatic aldehydes and the highest when a K base is used for aromatic aldehydes . When the reaction was performed at 0 °C, an even higher 94:6 selectivity was obtained in 95% yield (entry 14).…”

“…Although stereodefined synthesis of carbon–carbon double bonds with high selectivity is critically important in organic synthesis, the above methods only gave ( E )-α,β-unsaturated esters selectively. During our study on the Z -selective Horner–Wadsworth–Emmons (HWE) reaction, we prepared (ArO) 2 P­( O )­CH 2 CO 2 Et 1 , which gave ( Z )-α,β-unsaturated esters highly selectively. , Taylor and co-workers reported a one-pot oxidation/HWE reaction of benzyl alcohol with MnO 2 (10 equiv), our reagent (PhO) 2 P­( O )­CH 2 CO 2 Et 1a , and guanidine base in refluxing THF for 48 h to give ethyl cinnamate with only Z / E = 2:1 in 62% yield . Since the one-pot oxidation/olefination sequence is beneficial, we studied the one-pot procedure composed of oxidation of primary alcohols to aldehydes and the following Z -selective HWE reaction (Scheme ).…”