GBL synthesis starting from 1,3-Propanediol

[Rhodium]

Investigations of the Olefinic Acids. Part X.
The Formation of Lactones from Butenoic and Pentenoic Acids
E. J. Boorman & R. P. Linstead

J. Chem. Soc. 577-580 (1933)

(https://www.thevespiary.org/rhodium/Rhodium/pdf/gbl.hydroxynitrile.pdf)

Summary
Describes a synthesis of gamma-butyrolactone from trimethylene chlorohydrin and discusses lactone/acid equilibriums in aqueous solution.


A preparation of trimethylene chlorohydrin from 1,3-propanediol can be found in 

Organic Syntheses, CV 1, 533

(http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv1p0533)

[Rhodium]

Rates and Equilibria in the Reaction of gamma-Butyrolactone with Alcohols. A Convenient Synthesis of 4-Hydroxybutyrates
H. C. Brown and K. A. Keblys

J. Org. Chem 31, 485-487 (1966)

(https://www.thevespiary.org/rhodium/Rhodium/pdf/gbl.alcoholysis.equilibria.pdf)

Abstract
The acid-catalyzed alcoholysis of gamma-butyrolactone yields an equilibrium mixture of the lactone and the corresponding 4-hydroxybutyrates. Methyl, ethyl, and isopropyl esters of 4-hydroxybutyric acid were isolated in 10-50% yield. The relative rates of the acid-catalyzed reaction of gamma-butyrolactone with alcohols decrease in the order: methyl > ethyl > isopropyl. The equilibrium constants and the equilibrium concentrations of the corresponding 4-hydroxybutyrates have been determined.