Lactones regioselective ring-opening

A regioselective ring-opening reaction of A-tosylaziridincs with anilines followed by lactamization to form products such as 55 was reported <07TL2007>. Intramolecular lactonization to 3-arylidenelactone 56 was observed when the reaction was carried out in the... 

Likewise, the first step in the synthesis of 50 is a regioselective ring opening of epoxide 40 with organolithium compound 45. By a series of manipulations, sulfone 47c is produced in 50% overall yield with 97% ee [11]. Ring opening of lactone 48 with the lithiated sulfone 47c... 

The stereochemistry of ring-opening polymerizations has been studied for epoxides, episul-fides, lactones, cycloalkenes (Sec. 8-6a), and other cyclic monomers [Pasquon et al., 1989 Tsuruta and Kawakami, 1989]. Epoxides have been studied more than any other type of monomer. A chiral cyclic monomer such as propylene oxide is capable of yielding stereoregular polymers. Polymerization of either of the two pure enantiomers yields the isotactic polymer when the reaction proceeds in a regioselective manner with bond cleavage at bond 1. 

The reaction of phenols with the spiro /3-lactone (397), obtained from the reaction of diketene with ethyl diazoacetate, leads to coumarins (79JCS(Pl)525). Initial ring opening of the spiro compound to the diketo ester followed by regioselective intramolecular acylation would seem to be a possible mechanism (Scheme 129). 

Both stereo- and regioselectivity are better in ElcB reactions, such as the opening of this unsaturated lactone in base. The double bond inside the ring remains Zbut the new one, formed as the ring opens, prefers the E geometry, The transition state for the elimination step already has a product-like shape and prefers this for simple steric reasons. 

The synthesis of the (+ )-compactin lactone 30, an important component of the statins, illustrates the power of the dihydroxylation methodology when coupled with regioselective sulfite ring opening (Scheme 3.28) [339]. 

Reaction of the 2-methyl-substituted cyclopropane 2 with titanium(IV) chloride/3-phenyl-propanal gives a mixture of the 2-methyl- and 3-methyl-y-lactones 3 and 4, indicating that the mode of ring opening of this cyclopropane by titanium(IV) chloride lacks regioselectivity. ... 

Ethyl glucoside as a multifunctional initiator for enzyme-catalyzed regioselective lactone ring-opening polymerization. J. Am. Chem. Soc.,... 

---