Fe(III) halides as effective catalysts in carbon-carbon bond formation: synthesis of 1,5-dihalo-1,4-dienes, alpha,beta-unsaturated ketones, and cyclic ethers.
Iron(III) halides have proven to be excellent catalysts in the coupling of acetylenes and aldehydes. When terminal acetylenes were used the main products obtained were 1,5-dihalo-1,4-dienes with (E,Z)-stereochemistry contaminated in some cases with (E)-alpha,beta-unsaturated ketones. The former carbonyl derivatives were the sole products isolated when nonterminal aromatic alkynes were used. When homopropargylic alcohols were used, a Prins-type cyclization occurred yielding 2-alkyl-4-halo-5,6-dihydro-2H-pyrans. In addition, anhydrous ferric halides are also shown to be excellent catalysts for the standard Prins cyclization with homoallylic alcohols. Isolation of an intermediate acetal, calculations, and alkyne hydration studies provide substantiation of a proposed mechanism.
Miranda
Pedro O
PO
Instituto Universitario de Bio-Orgánica Antonio González and Departamento de Física Básica, Universidad de La Laguna, C/Astrofísico Francisco Sánchez s/n, 38206 La Laguna, Tenerife, Canary Islands, Spain.
Díaz
David D
DD
Padrón
Juan I
JI
Ramírez
Miguel A
MA
Martín
Víctor S
VS