The facile synthesis of a large ring lactone by acid-catalysed cyclisation of an (z)-ene-diyne hydroxy acid precursor.

Total Synthesis and Biological Evaluation of Zealactone 1a/b

“…[13] Subsequent Sonogashira coupling of vinyl bromide 13a with mono-TBS-acetylene resulted in poor yield of the desired enyne 15 employing a variety of conditions 1 . [14,15] Fortunately, the analogous vinyl iodide 13b could be synthesized by carbocupration-iodination of 14 in excellent yield and provided high reactivity in the subsequent Sonogashira coupling. Saponification of methyl ester 15 was achieved by using aqueous lithium hydroxide in tert-butanol.…”

1,2-Dihalogenalkenes: Useful Linchpins to Unsaturated Compounds via Palladium or Nickel Catalysis

“…If unsymmetrical enediynes were needed, reaction of (E)and (Z)-chloroenynes with alk-1-ynes in the presence of Pd(PPh 3 ) 4 -CuI leads stereospecifically to unsymmetrical (E)-and (Z)-enediynes in excellent yields. 39,50 The use of PdCl 2 (PhCN) 2 as catalyst in piperidine 51 for such reaction have been shown to be much more effective catalysts than Pd(PPh 3 ) 4 or PdCl 2 (PPh 3 ) 2 since large rate enhancements were observed reducing the reaction time to 0.5-2h at room temperature compared to 4-9h with Pd(PPh 3 ) 4 (Scheme 20). 40,51,52 Scheme 20 Scheme 17…”

“…In recent years, conjugated (Z)-enediynes have also been shown to be useful starting materials in the synthesis of various macrocyclic enediyne compounds. 4,5,58,59 Thus, when bearing appropriate functions, unsymmetrical (Z)enediynes can be efficiently used in the synthesis of enediyne 12-membered ring lactones 50 or lactams 60 by simple intramolecular cyclization of the corresponding w-hydroxy or amino acid precursor as described in Scheme 24.…”

“…Polyhalogenoalkenes are also useful starting material for the synthesis of substituted alkenes. Thus, Normant 99 has shown that dibutylzinc reacts with trichloroethene under vigorous conditions to afford mainly monosubstituted product 1,1-dichlorohex-1-ene (50) in moderate yield (33%). Under similar conditions, Normant 99 also observed that when the reaction was performed with propylmagnesium chloride in THF reflux a mixture of 1,1dichloropent-1-ene (51) (35%) and (Z)-1,2-dichloropent-1-ene 52 (12%) was obtained (Scheme 50).…”

Lactonization of ω-Hydroxycarboxylic Acids Using (4,5-Dichloro-6-oxo-6H-pyridazin-1-yl)phosphoric Acid Diethyl Ester

“…Although several useful methods have therefore been reported, [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] the research in this field still active even now.…”