β‐Alkyl‐α,β‐Unsaturated Esters from Enol Phosphates of β‐Keto Esters: Methyl 2‐Methyl‐1‐Cyclohexene‐1‐Carboxylate

Abstract

β‐Alkyl‐α,β‐unsaturated esters from enol phosphates of β‐keto esters: methyl 2‐methyl‐1‐cyclohexene‐1‐carboxylate intermediate: methyl 2‐oxocyclohexanecarboxylate intermediate: Methyl 2‐(diethylphosphoryloxy)‐1‐cyclohexene‐1‐carboxylate product: methyl 2‐methyl‐1‐cyclohexene‐1‐carboxylate byproduct: 1‐acetyl‐2‐methylcyclohexene solvent: petroleum ether

Mass Efficiency of Alkene Syntheses with Tri- and Tetrasubstituted Double Bonds

“…Therefore, a protocol such as the ynolate conversion (entry 21) producing a Z:E ratio of 99:1 could be more sensible than an alleged resource efficient alternative with worse selectivity. For example, the β-alkyl-α,β-unsaturated ester synthesis 100 via alkylcuprates is accompanied by the formation of a byproduct that could not be separated by flash chromatography.…”

High-yielding method for preparation of carbocyclic or N-containing heterocyclic β-keto esters using in situ activated sodium hydride in dimethyl sulphoxide

“…β-Keto esters are important synthetic precursors widely used in laboratory (1) and industrial syntheses (2,3). The compounds are very often prepared by the acylation of preformed ketone enolate anions using reagents such as Weinreb amides (4), alkyl-cyanoformates (5,6) or 1-Boc-imidazole (7), as well as alkyl carbonates at elevated temperature (8)(9)(10)(11). Dieckmann condensation (12) of various diesters provides good yields of 5-and 6-membered carbocyclic (13)(14)(15) or heterocyclic β-keto esters (16)(17)(18)(19)(20)(21) while acyclic analogues result from Claisen ester condensation (22) typically after prolonged heating in aromatic solvents with alkoxides.…”