Radical Cyclization in Heterocycle Synthesis. 12. Sulfanyl Radical Addition-Addition-Cyclization (SRAAC) of Unbranched Diynes and Its Application to the Synthesis of A-Ring Fragment of 1.ALPHA.,25-Dihydroxyvitamin D3.
Synthesis of Cyclic <i>cis</i>-Enediynes from Manganese Carbyne Complexes and α,ω-Diynes
作者:Charles P. Casey、Trevor L. Dzwiniel、Stefan Kraft、Ilia A. Guzei
DOI:10.1021/om0303799
日期:2003.9.1
Cyclic cis-enediynes are readily prepared by a two-step one-pot procedure. The first step is the copper-catalyzed addition of alpha,omega-diynes to manganese carbyne complexes to give intermediate bis(alkynylcarbene) complexes that rearrange to enediyne complexes below room temperature. In the second step, the free enediyne is released from manganese by photolysis, copper-catalyzed air oxidation, or stoichiometric Cu(II) oxidation. These new procedures have been applied to a variety of five-, six-, and seven-membered-ring cyclic enediynes containing a range of ether, ester, and ketone functional groups.
Au<sub>2</sub>O<sub>3</sub> as a Stable and Efficient Catalyst for the Selective Cycloisomerization of γ-Acetylenic Carboxylic Acids to γ-Alkylidene-γ-Butyrolactones
The high potential of commercially available Au2O3 as a catalyst in the cyclization of alkynes bearing carboxylic acids to the corresponding γ-alkylidene-γ-butyrolactones through a general, efficient and easy procedure is presented. The reaction shows a high degree of chemo-, regio-, and stereoselectivity. The 5-exo mode of cyclization and anti auration are a general trend for the Au2O3 catalyst.
Radical Cyclization in Heterocycle Synthesis. 12. Sulfanyl Radical Addition-Addition-Cyclization (SRAAC) of Unbranched Diynes and Its Application to the Synthesis of A-Ring Fragment of 1.ALPHA.,25-Dihydroxyvitamin D3.
作者:Okiko MIYATA、Emi NAKAJIMA、Takeaki NAITO
DOI:10.1248/cpb.49.213
日期:——
Sulfanyl radical addition-addition-cyclization (SRAAC) of unbranched diynes proceeded smoothly to give cyclized exo-olefins, while the sulfanyl radical addition-cyclization-addition (SRACA) of diynes having a quaternary carbon gave cyclized endo-olefins. This method was successfully applied to the synthesis of A-ring fragment of 1α, 25-dihydroxyvitamin D3.