M.C. White, Chem 153 UE-Allyl chemistry -349 Week of December 2. 2002 Carbon and oxygen spirocycles yclizations CO,Et O,Et Pd(PPh3) 7 mol% COet NaH,THF,65°C note that attack at the least sition results in a bridgehead olefin: Ln(Oac)Pd Pd(PPh3)47 mol% NaH. THF. 65C CO,Me CO,Me >99% Godleski JOC 1982(47)383 OrMe cis-fused decalin systems RO,O CO RO2C COrR=E NaH. THF. 65%C NaH. THF 65C CO,R CO,R Aco complements the Robinson annulation 75%.>98%cis >98%cis approach which generally leads to Backwall TL 1989(30)61 reyiew on cyclizations: Trost. ACIEE 1989(2811173 Macrocyclizations occur readily Regioselectivity favors substitution at the least sterically hindered carbon, particularly when bulky nucleophiles are used. TESO, OTES OTES LOTUS H3C Pdzdbas 10 mol% TESO OtBu OMe HO THF.40°C.12h 80% for IMSC Sorenson JACS2002(124)4552 (+}FR82877M.C. White, Chem 153 π-Allyl chemistry -349- Week of December 2, 2002 Carbon and oxygen spirocycles: Cyclizations OAc CO2Et CO2Et CO2Et CO2Et OAc O CO2Me O CO2Me O CO2Me Ln(OAc)PdII Pd(PPh3)4 7 mol% NaH, THF , 65oC 66% note that attack at the least sterically hindered position results in a bridgehead olefin: Pd(PPh3)4 7 mol% NaH, THF , 65oC >99% Godleski JOC 1982 (47) 383. O TESO OTES TMSO O Ot-Bu O O OMe O OTMS O O-tBu TESO OTES 19-membered ring formation Pd2dba3 10 mol% THF, 40oC, 12h 80% O O O H H CH3 H CH3 H OH H3C HO CH3 H H H H (+)-FR182877 Macrocyclizations occur readily. Regioselectivity favors substitution at the least sterically hindered carbon, particularly when bulky nucleophiles are used. Sorenson JACS 2002 (124) 4552. cis-fused decalin systems: AcO O CO2R Pd2dba3/PPh3 cat NaH, THF, 65oC RO2C CO2R H H E E O E >98% cis complements the Robinson annulation approach which generally leads to trans-fused rings. AcO O CO2R CO2R RO2C = E Pd2dba3/PPh3 cat NaH, THF, 65oC O E E E H H 75%, >98% cis Backvall TL 1989 (30) 617. review on cyclizations: Trost ACIEE 1989 (28) 1173