Diynes heterocyclics, 5-membered

For larger rings, heteracycloalkane or heteraannulene are used for example, 10 will be called 1,6-ditelluracyclodo-decane, while 11 will be 2,ll-diselena[3.3]metacyclophane. The last ring mentioned here is exemplified by 12, which is a 15-member heterocycle containing four atoms of selenium it is called l,4,8,ll-tetraselena-cyclopentadeca-2,9-diyne. 

Key to method (A) exchange reaction with tin heterocycle (B) hydride addition to diyne (C) oxidation of saturated ketone (D) bromination-dehydrobromination by pyrolysis (E) reaction of RLi or ArLi with exocyclic M-Cl of preformed diene (F) ring expansion reaction from cyclopentadiene derivative (G) LiAlHi reduction of exocyclic M-Cl (H) carbene insertion into five-membered cyclo-pentadiene derivative. Doering-Hoffman method (I) 1,6-cycloaddition of GeCU. 

Equation 1.32 [28]. Thus, nicely functionalized five- and six-membered carbocyclic and heterocyclic rings derive simply by an atom economic addition of water to a suitable diyne. The ease of accessing such diynes makes this methodology particularly attractive. 

As 1,/2-alkenes, 1,6-derivatives are used very frequently leading to five-membered heterocycles, while the use of 1,7-derivatives, which produce six-mem-bered heterocycles, is very rare. The reactions of 1,6-dienes, -enynes, and -diynes are classified into three groups (a) cycloisomerization, (b) tandem addition— cyclization, and (c) cycloaddition, such as the Pau-son—Khand reaction, cyclotrimerization, and the Diels—Alder reaction (Scheme 15).97 In these reactions five-membered heterocycles are constructed upon the carbon—carbon bond-forming processes. 

Transition metal-catalyzed carbocyclization of nitrogen- and oxygen-tethered 1, n-enynes and diynes to give five- or six-membered heterocyclic compounds 12CC10271. 

The Pd-catalysed aerobic 2- -2- -2-cycloaddition of 1,6-diynes and acrylates produced polysubstituted five-membered aromatic carbocycles/heterocycles in good to... 

Wilckens, K., Uhlemann, M. and Czekehus, C. 2010. Gold-catalyzed cnseven-membered ring heterocycles. Chem. Eur. J. 15 13323-13326. 

To study the effect of the cinnoline heterocycle on the reactivity of 10-membered enediynes, the rates of Bergman cyclization of compound 3.824 and 3,4-benzocyclodeca-l,5-diyne-7-ol 3.827 were compared at 75°C in 2-propanol. The products were analyzed by high-performance liquid chromatography (HPLC). The reaction obeys first-order kinetics and enediyne 3.824 is four orders of magnitude more active than benzo-fused analog 3.827 [381a]. 

Carbocyclization of 1,5- and 1,6-diynes has been reported leading to benzopyrones [142] and Z-cyclopentylidenes [143, 144], respectively. Furthermore, 1,4-diynes 44 react in the presence of gold-catalysts to form seven-membered ring heterocycles 45 by an endo-cyclization (Scheme 18) [145]. 

---