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14.3.1.4.3.1 Method 1: Halogen–Metal Exchange

DOI: 10.1055/sos-SD-014-00183

Afarinkia, K.; Vinader, V.Science of Synthesis, (200314308.

In contrast to direct metalation (see Section 14.3.1.4.1.2), halogenmetal exchange is widely used for the preparation of metallo derivatives of 2H-pyran-2-ones. No information regarding the relative stability of the ring positional isomers of metallo derivatives of 2H-pyran-2-ones is available. Since mainly the 3- and 5-halo derivatives of 2H-pyran-2-ones are known, generally the 3- and 5-metallo derivatives have been prepared and explored. There is no evidence of anion migration in these derivatives. In fact, the 3-cuprio derivative 71 of 2H-pyran-2-one, prepared from the 3-lithio derivative (see Scheme 63), is particularly interesting as it is quite stable and does not undergo reductive dimerization at all.[‌207‌] The stannyl derivatives have been synthesized via a cycloaddition reaction (see Section 14.3.1.1.3.1); however, a more general synthesis is through palladium-catalyzed stannylation (Scheme 64).[‌6‌]

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