Bifunctionalized allenes. Part xvii. Synthesis of 2,5-dihydro-1,2-oxaphospholes and 4-phosphoryl-3,6-dihydro-2h-pyrans by electrophilic cyclization and coinage metal-catalyzed cycloisomerization of phosphorylated -hydroxyallenes

Research Article
Christov. VC, Ismailov. IE and Ivanov. IK
Phosphorylated - hydroxyallenes, electrophilic cyclization, 2,5-dihydro-1,2- oxaphospholes, coinage metalcatalyzed cycloisomerization, 3,6-dihydro-2H-pyrans.

A convenient and efficient regioselective synthesis of phosphorylated -hydroxyallenes by an atomeconomical [2,3]-sigmatropic rearrangement of the mediated propargyl phosphite or phosphinite whichcan be readily prepared via reaction of protected 5-methyl-dec-6-yn-5-ol with dimethyl chlorophosphite orchlorodiphenyl phosphine respectively is described. This paper discusses a reaction of phosphorylated -hydroxyallenes with protected or unprotected hydroxy group involving 5-endo-trig cyclization. Reaction of dimethyl [1-(2-hydroxypropyl)-3-methyl-hepta-1,2-dienyl] phosphonates with electrophiles that produces 2-oxo-2,5-dihydro-1,2-oxaphospholes due to the participation of the phosphonate neighboring group in the cyclization is described. On the other hand, hept-(1E)-en-1-yl phosphine oxides were prepared as mixtures with 2,5-dihydro-1,2-oxaphosphol-2-ium chlorides in a ratio of about 1:2 by chemo-,regio-, and stereoselective electrophilic addition to the C2-C3-double bond in the allene moiety and subsequent concurrent attack of the external (chloride anion) and internal (phosphine oxide group)nucleophiles. Phosphorylated -hydroxyallenes were smoothly converted into the corresponding 4-phosphoryl-3,6-dihydro-2H-pyrans by using 5 mol % of coinage metal salt as catalyst in 6-endo-trigcycloisomerization reaction.