Cyclic Alkynes: Preparation and Properties

Shape-Persistent, Nano-Sized Macrocycles

“…This excludes important work by Hodge, [9] de Meijere, [10] Stoddart, [11] and others. [12] Though many of these cycles will be shape-persistent to some degree, those with a methylene carbon atom, ether group, or similar component are regarded as conformationally less rigid than the cases reported here, in which all integral ring members are unsaturated. The aspect of shape persistency may be assessed differently by different researchers.…”

Studies on synthesis of optically active twelve-membered diynes: a convergent construction of a twelve-membered diketodiyne compound with C2 symmetry

“…For the initial evaluation of this strategy, our effort was focused on the development of an efficient method for the construction of 7 starting from inexpensive -mannitol (9) and diethyl -tartrate (10). At the outset, -mannitol (9) was converted into the C 2 symmetric known diepoxide 11 11 (Scheme 2) possessing the vicinal two methoxy functionalities that would be suitable for our purpose.…”

“…According to our retrosynthetic analysis (Scheme 1), we next investigated a coupling reaction of the diyne 4 with a chiral dialdehyde with C 2 symmetry (e.g., an antipode of 6). Diethyl -tartrate (10) was converted into the known dihydroxy compound 26, 21 which was subsequently treated with tert-butyldimethylsilyl (TBDMS) chloride in THF in the presence of sodium hydride (NaH) to afford 27 in 71% yield (Scheme 5). The coupling reaction of the diyne 13 with the aldehyde freshly derived from 27 was carried out as follows: treatment of 13 with lithium hexamethyldisilazide (LHMDS) in THF at Ϫ78 ЊC in the presence of anhydrous cerium() chloride (CeCl 3 ) 22 generated the dicerium acetylide in situ, which was then exposed to the aldehyde, obtained from 27 by Swern oxidation, affording 28 in 65% yield as a mixture of two diastereoisomers in a ratio of 59 : 41.…”

“…In summary, we have developed a procedure for the preparation of the optically active twelve-membered diketodiyne derivative 35 with C 2 symmetry starting from the commercially available diethyl -tartrate (10). Since the diketodiyne derivative 35 possesses two benzoyloxy groups at the C-4 and C-5 positions from which the epoxy functionality may be formed, it is regarded as a suitable precursor for the bicyclo[7.3.0]dodecadienediyne framework, a core of the NCS chromophore 1.…”

Cyclization Reactions of Coordinated Alkynes in Tungsten(II) Complexes

“…Cycloalkynes, with their synthetically versatile carbon−carbon triple bond, are important synthetic targets . Strategies for alkyne synthesis normally apply to straight chains and often do not provide for cyclic analogs .…”