Isotopically unmodified reference compounds bis(methylsulfanyl)methane
and furan-2(5H)-one were purchased from Merck (Darmstadt,
Germany). (2H8)Naphthalene was also from Merck.
(2H8)Bis(methylsulfanyl)methane was synthesized
as detailed in the literature.29 (link) (2H2)Furan-2(5H)-one was synthesized
according to a procedure published previously30 (link) but with some modifications. In brief, 3a,4,7,7a-tetrahydro-4,7-epoxy-2-benzofuran-1,3-dione
(abcr, Karlsruhe, Germany) was deuterated with sodium borodeuteride
(Cambridge Isotope Laboratories, Tewksbury, MA, USA) under an argon
atmosphere. Acidic workup led to the intermediate (3,3-2H2)-3a,4,7,7a-tetrahydro-4,7-epoxy-2-benzofuran-1(3H)-one, which was extracted by dichloromethane instead of
chloroform and then purified by chromatography (3 cm column diameter)
on silica gel 60 (0.040–0.063 mm; VWR, Darmstadt, Germany;
60 g). After being washed with n-hexane/ethyl acetate
(50/50, v/v; 150 mL), the compound was eluted with n-hexane/ethyl acetate (25/75, v/v; 150 mL) and ethyl acetate (200
mL). The solvents were removed in vacuo, and the purified (3,3-2H2)-3a,4,7,7a-tetrahydro-4,7-epoxy-2-benzofuran-1(3H)-one was heated to 150 °C at 15 mbar to distill off
the target product (5,5-2H2)furan-2(5H)-one (96% purity by GC–flame ionization detector)
obtained in a retro-Diels–Alder reaction.
and furan-2(5H)-one were purchased from Merck (Darmstadt,
Germany). (2H8)Naphthalene was also from Merck.
(2H8)Bis(methylsulfanyl)methane was synthesized
as detailed in the literature.29 (link) (2H2)Furan-2(5H)-one was synthesized
according to a procedure published previously30 (link) but with some modifications. In brief, 3a,4,7,7a-tetrahydro-4,7-epoxy-2-benzofuran-1,3-dione
(abcr, Karlsruhe, Germany) was deuterated with sodium borodeuteride
(Cambridge Isotope Laboratories, Tewksbury, MA, USA) under an argon
atmosphere. Acidic workup led to the intermediate (3,3-2H2)-3a,4,7,7a-tetrahydro-4,7-epoxy-2-benzofuran-1(3H)-one, which was extracted by dichloromethane instead of
chloroform and then purified by chromatography (3 cm column diameter)
on silica gel 60 (0.040–0.063 mm; VWR, Darmstadt, Germany;
60 g). After being washed with n-hexane/ethyl acetate
(50/50, v/v; 150 mL), the compound was eluted with n-hexane/ethyl acetate (25/75, v/v; 150 mL) and ethyl acetate (200
mL). The solvents were removed in vacuo, and the purified (3,3-2H2)-3a,4,7,7a-tetrahydro-4,7-epoxy-2-benzofuran-1(3H)-one was heated to 150 °C at 15 mbar to distill off
the target product (5,5-2H2)furan-2(5H)-one (96% purity by GC–flame ionization detector)
obtained in a retro-Diels–Alder reaction.