SummaryMulticomponent reactions (MCRs) are one of the most important processes for the preparation of highly functionalized organic compounds in modern synthetic chemistry. As shown in this review, they play an important role in organophosphorus chemistry where phosphorus reagents are used as substrates for the synthesis of a wide range of phosphorylated heterocycles. In this article, an overview about multicomponent reactions used for the synthesis of heterocyclic compounds bearing a phosphonate group on the ring is given.

Dialkyl 2-(alkylamino)-4,9-dihydro-9-oxocyclohepta [b]pyran-3,4-dicarboxylates are prepared in a one-pot three-component reaction of alkyl isocyanide, dialkyl acetylenedicarboxylate, and a-tropolone (¼ 2-hydroxycyclohepta-2,4,6-trienone). The reaction proceeds smoothly at room temperature and under neutral conditions to afford tropolone derivatives in high yield.Introduction. -Heterocycle-fused tropolones, an important class of compounds with varied pharmacological and biological properties have attracted great attention since the beginning of tropoid chemistry [1 -4]. The cyclohepta [b]pyran ring system is the backbone of some natural products such as paulitine (Fig.), which displays several biological activities, and some derivatives of this system exhibit platelet anti-aggregating, HIV protease inhibition, anesthetic, histaminic response-reducing, antimalarial, anti-inflammatory, and analgesic activities [5 -8]. . Also the reaction of chloro(phenyl)ketene with 2-(aminomethylidene)cycloheptanones, followed by dehydrochlorination of the primary adducts, yields 4-amino-6,7,8,9-tetrahydro-3-phenylcyclohepta[b]pyran-2(5H)-ones [14].

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