The influence of distal substitution on the base-induced isomerization of long-chain terminal alkynes

Improved Rigidin-Inspired Antiproliferative Agents with Modifications on the 7-Deazahypoxanthine C7/C8 Ring Systems

“…This type of isomerization is generally achieved through use of moderately strong bases at high temperatures (>100 °C). A literature search revealed that this reaction has typically been achieved using potassium tert -butoxide in DMSO at low/moderate temperatures, or by the use of KOH in water or ethanol at high temperatures (for a noncomprehensive set of examples, see refs − ). Reaction conditions involving the use of NaOEt in DMSO at elevated temperatures (90 °C–100 °C) for this type of isomerization were not found during the literature search.…”

Total Synthesis of Natural Lembehyne C and Investigation of Its Cytotoxic Properties

“…It is noteworthy that the synthesis of the key monomer (6 Z )-tricosa-1,2,6-triene is a fairly complicated task; therefore, two approaches were developed for its synthesis from commercially available 1-bromohexadecane ( 2 ) (Scheme ) or 4-pentyn-1-ol ( 11 ) (Scheme ). The former approach comprising eight steps involves the reaction of 1-bromohexadecane ( 2 ) with the lithium acetylide ethylenediamine complex in DMSO to give 1-octadecyne ( 3 ) in 93% yield . Compound 3 is treated with EtMgBr in THF at reflux for 3 h to give the corresponding magnesium acetylide 4 , which reacts with ethylene oxide and then undergoes acid hydrolysis to give eicos-3-yn-1-ol ( 5 ).…”

“…The former approach comprising eight steps involves the reaction of 1-bromohexadecane (2) with the lithium acetylide ethylenediamine complex in DMSO to give 1octadecyne (3) in 93% yield. 11 Compound 3 is treated with EtMgBr in THF at reflux for 3 h to give the corresponding magnesium acetylide 4, which reacts with ethylene oxide and then undergoes acid hydrolysis to give eicos-3-yn-1-ol (5). Next, (3Z)-eicos-3-en-1-ol (6) was synthesized via Ni(OAc) 2catalyzed hydrogenation of alkynol 5; then alcohol 6 was treated with MeSO 2 Cl in CH 2 Cl 2 for 4 h to give mesylate 7, which was converted to 1-bromo-(3Z)-eicos-3-ene (8) in 85% yield by refluxing with LiBr in acetone for 3 h. The final stage included preparation of alkyne 9 by the reaction of alkenyl bromide 8 with lithium acetylide ethylenediamine complex and the subsequent acetylene−allene rearrangement of alkyne 9 under Mannich reaction conditions to afford the target (6Z)tricosa-1,2,6-triene (10).…”

“…The alternative (five-step) method proposed for the synthesis of (6Z)-tricosa-1,2,6-triene (10) is based on 4-pentyl-1-ol (11) as the starting material. By successive treatment with n-BuLi and 1-bromohexadecane, this compound was converted to 4heneicosyn-1-ol (12), which was subjected to catalytic hydrogenation with molecular hydrogen in the presence of Ni(OAc) 2 to afford 4Z-heneicos-4-en-1-ol (13) in 85% yield over two steps (Scheme 3).…”