Sulfur- and selenium-promoted cyclization of allenic phosphonates and phosphinates to substituted 1,2-oxaphosphol-3-enes: stereochemical consequences at phosphorus. The crystal and molecular structure of (Z)-3,5-di-tert-butyl-2-methoxy-4-(phenylseleno)-1,2-oxaphosphol-3-ene 2-oxide

Fifty Years of (Benz)oxaphospholene Chemistry

“…[74] Alternatively, phosphono pentadienes can serve as precursors for the electrophile-induced synthesis of oxaphospholenes as well. [78,79,81,84,85] Unsubstituteda llenylphosphonates did not produce oxaphospholenic cyclizationp roductsa nd only yielded 1,2-adducts 98 or 2,3-adducts 99. [75,76] Not only halogen sources could initiate cyclization of allenylphosphonates 96.S ulfenyl-, [77][78][79][80][81] selenyl- [52,[82][83][84][85][86][87] or tellurylhalides [88,89] efficiently gave rise to 4-chalcogeno oxaphospholenes 97 (Scheme 21).…”

“…[72] Competitive reactionsa lso occurred when the phosphonyl group is in g-position with respectt ot he carboxyl function. [75,76] Not only halogen sources could initiate cyclization of allenylphosphonates 96.S ulfenyl-, [77][78][79][80][81] selenyl- [52,[82][83][84][85][86][87] or tellurylhalides [88,89] efficiently gave rise to 4-chalcogeno oxaphospholenes 97 (Scheme 21). [74] Alternatively, phosphono pentadienes can serve as precursors for the electrophile-induced synthesis of oxaphospholenes as well.…”

“…[73] Treatment of 1-phosphoryl-1-sulfinate-2,3-butadiene 89 b similarly yielded am ixture of two heterocycles, which could each be isolateds eparately. In reaction with sulfenylhalides, 1,3,3-trisubstituted and 1,3-disubstituted allenylphosphonates exclusively yieldedt he oxaphospholene cyclization products 97, [80,81] while 3,3-disubstitued allenylphosphonates also gave small amountso f1 ,2-adducts 98 of the sulfenylchloridei ns ome cases. The terminal alkene in the 2-phosphonopentadiene 94 is activatedb yt he electrophile, whichi sf ollowed by ring closure through intramolecular attack of the phosphoryl group onto the internal double bond (Scheme 20).…”

“…The terminal alkene in the 2-phosphonopentadiene 94 is activatedb yt he electrophile, whichi sf ollowed by ring closure through intramolecular attack of the phosphoryl group onto the internal double bond (Scheme 20). [75,76] Not only halogen sources could initiate cyclization of allenylphosphonates 96.S ulfenyl-, [77][78][79][80][81] selenyl- [52,[82][83][84][85][86][87] or tellurylhalides [88,89] efficiently gave rise to 4-chalcogeno oxaphospholenes 97 (Scheme 21). In reaction with sulfenylhalides, 1,3,3-trisubstituted and 1,3-disubstituted allenylphosphonates exclusively yieldedt he oxaphospholene cyclization products 97, [80,81] while 3,3-disubstitued allenylphosphonates also gave small amountso f1 ,2-adducts 98 of the sulfenylchloridei ns ome cases.…”

“…[75,76] Not only halogen sources could initiate cyclization of allenylphosphonates 96.S ulfenyl-, [77][78][79][80][81] selenyl- [52,[82][83][84][85][86][87] or tellurylhalides [88,89] efficiently gave rise to 4-chalcogeno oxaphospholenes 97 (Scheme 21). In reaction with sulfenylhalides, 1,3,3-trisubstituted and 1,3-disubstituted allenylphosphonates exclusively yieldedt he oxaphospholene cyclization products 97, [80,81] while 3,3-disubstitued allenylphosphonates also gave small amountso f1 ,2-adducts 98 of the sulfenylchloridei ns ome cases. [78,79,81,84,85] Unsubstituteda llenylphosphonates did not produce oxaphospholenic cyclizationp roductsa nd only yielded 1,2-adducts 98 or 2,3-adducts 99.…”