1999 organo-phosphorus compounds, nonmetal heterocycles

organo-phosphorus compounds, nonmetal heterocyclesS 0087

28 - 206Organophosphorus Compounds. Part 138. 3,5-Dimesityl-1,2,4-oxadiphosphole – Synthesis and Reactivity of a Novel Heterocycle.— The first synthesis of a 1,2,4-oxadiphosphole (II) is achieved on vacuumthermolysis of mesitylphosphaalkene (I). Compound (II) exhibits a greatpotential for cycloadditions. Thus, reaction of oxadiphosphole (II) with twoequivalents of phosphaalkynes (V) proceeds by initial regiospecific [4 + 2]cycloaddition to furnish an unsymmetrical oxatriphosphanorbornadiene whichregioselectively undergoes a second cycloaddition step to afford a mixture ofnovel regioisomeric oxatetraphosphadeltacyclenes (VI) and (VII). These adductsundergo a regiospecific [4 + 1] cycloaddition to o-benzoquinone (VIII) to givethe spiro compounds (IX) and (X). With dimethyl acetylenedicarboxylate (III),initial [4 + 2] cycloaddition and retro Diels–Alder reaction provides the firstaccess to a 1,2-oxaphosphole (IV) which cannot be isolated. An unexpectedreaction of compound (II) with azet (XI) affords a novel heterocyclic system(XII). — (MACK, ANDREAS; BERGSTRAESSER, UWE; REISS, GUIDOJ.; REGITZ, MANFRED; Eur. J. Org. Chem. (1999) 3, 587-595; FachbereichChem., Univ. Kaiserslautern, D-67663 Kaiserslautern, Germany; EN)

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