The Malonic Ester Synthesis with Styrene Oxide and with Butadiene Oxide¹

The Influence of the 2-Alkoxy Group and of C-5 Substituents on the Direction of Reductive Cleavage of 2-Alkoxytetrahydrofurans by AlH2Cl in Ether Solution

“…cis-trans-2-Methoxy-5-phenyltetrahydrofuran y-Phenyl-y-butyrolactone was prepared by the reaction of styrene oxide (21) with diethyl malonate as described (22) but with sodium hydride in 1,2-dimethoxyethane under nitrogen as the condensing system; yield, 54%; b.p. 123" at 0.8 mm; qi3 1.5392; lit.…”

“…That a polar effect of the alkyl group is still operative, although it is unable to manifest itself in terms of the direction of reductive cleavage, is clearly shown by the competitive reaction of a 1 : 1 mixture of 2-ethoxy-and 2-t-butoxytetrahydrofuran with a limited amount of AlH2Cl, sufficient to hydrogenolyze only one-half of the total acetal. It was found again that only ring cleavage products were obtained, but the ratio of the 2-t-butoxyto 2-ethoxytetrahydrofuran reduced was 78 : 22 effective in facilitating attainment of the transition state leading to oxocarbonium ion formation.…”

Direction of Ring Opening of Styrene Oxide and Butadiene Monoxide by Ester Carbanions†

“…Since we required a pure sample of lactone 10i for another purpose, we attempted its preparation using the reaction conditions of Russell and VanderWerf. 3 In fact, this procedure gave us a 30:70 mixture of 10i and 11i with an overall yield of 54%. The two isomers were cleanly separated by preparative HPLC and were identi®ed by their 1 H NMR spectra.…”

“…Reaction of 3 with the vinyl epoxide 2 was claimed also to take place exclusively at the primary epoxide carbon atom to give 10i 3,4 and this assertion has also received wide acceptance; 1,6,7 similarly the reaction of sodiocyanoacetate with styrene oxide 1 13 and with butadiene monoxide 2 13 was claimed to proceed by attack on the terminal carbon to give the products 10h and 10i respectively. In these cases the reactions do not appear to have been studied thoroughly since: there is one report 11 in which styrene oxide 1 has been shown to give both 3-and 4-phenyl lactones on reaction with cyanoacetate 5, though there is some confusion regarding the melting points given in this report (see below).…”

“…Styrene oxide 1 and butadiene monoxide (3,4-epoxybut-1ene) 2 have been used extensively in the investigation of the in¯uence of conjugative eects on the direction of ring opening of epoxides by nucleophiles 1,2 but the results have been confused by structural misassignments and failure to identify some signi®cant products. Early workers, 3,4 who did not have available the bene®ts of modern analytical methods, claimed that diethyl sodiomalonate 3 attacks 1 exclusively at the terminal carbon to give eventually the 4-phenyl lactone 10h via the sequence shown (Scheme 1). This ®nding was widely quoted 1,5±7 but later shown to be incorrect, evidence being obtained that both 10h and 11h are formed in signi®cant amounts, 8±11 though one worker 12 obtained only 11h via the isolated acid 9g.…”