In general, if the atoms that make up the ring contain heteroatoms, such rings become heterocycles, and organic compounds containing heterocycles are called heterocyclic compounds. An article called Synthesis of Cyclopentenones through Rhodium-Catalyzed C-H Annulation of Acrylic Acids with Formaldehyde and Malonates, published in 2021-07-02, which mentions a compound: 16400-32-1, Name is 1-Bromo-2-pentyne, Molecular C5H7Br, Category: tetrahydropyran.
An efficient rhodium-catalyzed protocol for the synthesis of cyclopentenones I (R1 = Et, Bn, c-hexyl, etc.; R2 = H, Me, Et, Ph; -R1R2- = -(CH2)3-, -(CH2)4-; R3 = Me, Et, n-Pr, i-Pr, n-Bu) based on a three-component reaction of acrylic acids, formaldehyde, and malonates via vinylic C-H activation is reported. Exploratory studies showed that 5-alkylation of as-prepared cyclopentenones could be realized smoothly by the treatment of a variety of alkyl halides with a Na2CO3/MeOH solution Excess formaldehyde and malonate led to a multicomponent reaction that afforded the multisubstituted cyclopentenones II (R1 = n-Bu, 3-FC6H4, Ph(CH2)2, etc.; R2 = H, Me, Et, etc.; R3 = Me, Et, n-Pr, i-Pr; -R1R2- = -(CH2)4-) through a Michael addition
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Reference:
Tetrahydropyran – Wikipedia,
Tetrahydropyran – an overview | ScienceDirect Topics