2- Methyl-2-vinyloxirane

Isopropenyl)oxirane (10.113, Fig. 10.26) and 2-methyl-2-vinyloxirane (10.114) were hydrolyzed by EH to the corresponding diols (10.116 and 10.117, respectively). Nucleophilic ring opening took place at the less-hindered, unsubstituted C-atom, with retention of configuration at C(2). (2R)-2-(Isopropenyl)oxirane was a better substrate than the (25)-enantiomer. Substrate enantioselectivity was more modest in the hydration of 2-methyl-2-vin-yloxirane (10.114), since this compound is chemically more reactive and undergoes partly nonenzymatic hydrolysis. 

The addition of 2-methyl-2-vinyloxirane to / -keto esters in the ptesence of a palladium catalyst and a chiral phosphine ligand proceeds regio- and stereoselectively to give 2-hydroxytetrahydrofuran-3-carboxylates (Equation 93) <2001JA12907>. 

Dienols. A mixture of 2-methyl-2-vinyloxirane, tri- -butylvinylstannane, and a little PdCl2(MeCN)2 in DMF containing 10 eqs. water allowed to react at room temp, until reaction complete-> product. Y 80% (100% 1,4-addition). Regio- and geo-selectivity was improved in the presence of water, other additives being less effective. Phenyl and styryl as well as vinyl groups were readily transferred. F.e. and 3-ethylene-alcohols s. A.M. Echavarren et al., J. Am. Chem. Soc. 110, 4039-41 (1988). 

MHz H-NMR spectrum of 2-methyl-2-vinyloxirane.The two H atoms on the oxirane ring are nonequivalent, so they exhibit geminal coupling. 

Tree diagrams that indicate the complex coupling seen in H-NMR signals for the vinyl group and the oxirane ring H atoms of 2-methyl-2-vinyloxirane. 

It has been observed quite long ago, that small amounts of water improved the selectivity of the phenylation of 1-methyl-l-vinyloxirane (Scheme 6.27) [61]. Both the relative amount of the rearranged product and the E/Z ratio were increased in aqueous DMF. 

Seebach and cowotkers reported that the doubly lithiated 2-propenethiol (13) reacts preferentially in the y-position with a variety of electrophiles, including aldehydes and ketones. The selectivity is 67-15%P The magnesium derivative (14), readily accessible by addition of MgBr2 (1 equiv.), reacts with aldehydes and ketones to give a-adducts almost exclusively (more than 90%). Successive addition of a saturated or a,p-unsaturated aldehyde or ketone followed by methyl iodide to a solution of the magnesium derivative at -80 °C affords very high yields of the a-adducts, which are synthetic precursors for vinyloxiranes (Scheme 5). ... 

The acid-sensitive hydroxyl group was protected as an O-thiocarbamate, and treatment of the resulting vinyloxirane 49 with catalytic amounts of trifluoroacetic acid (TFA) afforded the substituted-dihydrofuran derivative 50 in high yield. Free-radical deoxygenation followed by the cleavage of the methyl ethers conpleted the synthesis. 

VO, 2-vinyloxirane and MVO, methyl vinyl oxirane. Structure of EPN is shown in Scheme 10. 

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