Tetrahydro-2-bromo-2//-pyran

Propionic acid, 2-iodo-3-nitro-, ethyl ester [Propanoic acid, 2-iodo-3-mtro-, ethyl ester], 65 2//-Pyran, 3,4-dihydro-, 51 2//-PYR AN-2-ONE, 49 2H Pyran 2-one, 5 bromo 5,6-dihydro, 50 27/-PYRAN-2-ONE, 5,6 DIHYDRO-, 49 PYRIDINE, 2,3,4,5 TETRAHYDRO, 118 Pyridines, -substituted, 34 a Pyrone-6-carboxyhc acid [2H Pyran-6-Larboxyhc acid 2-oxo ], 51 Pyrroles, 34... 

TLC analysis was carried out on precoated plastic silica gel plates (with fluorescent indicator) using diethyl ether as eluant. With this eluant, the R of starting material is 0.50 and the Ri of 3,4-dibromo-3,4,5,6-tetrahydro-2(H)-pyran-2-one is 0.83. In addition to these two spots, a third spot, R = 0.55, corresponding to 3-bromo-5,6-dihydro-2(H)-pyran-2-one was detected. TLC analysis is not always reliable and it is better to analyze a small aliquot by NMR. 

A 50%-mineral oil dispersion of NaH added to a stirred soln. of 0-(tetrahydro-pyran-2-yl)mandelonitrile in dry dimethyl sulfoxide, after 1.5 hrs. 1-bromo-heptane added, stirred 2 hrs., then poured into ice-cold 10%-HCl octano-phenone. Y 83%. F. e. s. A. Kalir and D. Balderman, Synthesis 1973, 358. 

The tetrahydropyranyl derivative of propaigyl alcohol, tetrahydro-2-(2-propynyloxy)-2/f-pyran, can be converted to methyl 4-hydroxy-2-butynoate in four steps. Diethyl [(2-tetrahydropyranyloxy)methyl]phosphonate is a convenient Wadsworth-Emmons reagent. Tetrahydropyranyl esters of a-bromo acids can be used in the Reformatsky reaction for the preparation of (3-hydroxy acids. Elimination of a tetrahydropy-ranyloxy moiety from butyne-l,4-diols with lithium hydride constitutes an efficient method for the synthesis of allenic alcohols. ... 

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