TY - JOUR

T1 - Ring-Closing Metathesis of Co2(CO)6−Alkyne Complexes for the Synthesis of 11-Membered Dienediynes: Overcoming Thermodynamic Barriers

AU - Данилкина, Наталья Александровна

AU - Ляпунова, Анна Геннадьевна

AU - Хлебников, Александр Феодосиевич

AU - Старова, Галина Леонидовна

AU - Bräse, Stefan

AU - Балова, Ирина Анатольевна

PY - 2015

Y1 - 2015

N2 - The feasibility of ring-closing metathesis (RCM) as asynthetic entry to 10- and 11-membered dienediynes fused to abenzothiophene core was explored by experimental and theoreticalinvestigations. An established sequence of iodocyclization of o-(buta-1,3-diynyl)thioanisoles followed by Sonogashira coupling to form diethynylbenzothiopheneswas used to synthesize terminal benzothiophene-fusedenediyne diolefins as substrates for RCM. Encountering an unexpectedlack of reactivity of these substrates under standard RCM conditions, weapplied DFT calculations to reveal that the underlying cause was a positivechange in Gibbs free energy. The change in Gibbs free energy was also foundto be positive for RCM of indole- and benzannulated terminal diolefins whenaffording smaller than 12-membered rings. We found that modification of theenediyne−diolefin substrate as the Co2(CO)6−alkyne complex allowed thetarget benzothiophene-fused 11-membered dienediyne to be obtained viaRCM; the alkyne complexation strategy therefore provides one valid technique for overcoming challenges to macrocyclization ofthis kind.

AB - The feasibility of ring-closing metathesis (RCM) as asynthetic entry to 10- and 11-membered dienediynes fused to abenzothiophene core was explored by experimental and theoreticalinvestigations. An established sequence of iodocyclization of o-(buta-1,3-diynyl)thioanisoles followed by Sonogashira coupling to form diethynylbenzothiopheneswas used to synthesize terminal benzothiophene-fusedenediyne diolefins as substrates for RCM. Encountering an unexpectedlack of reactivity of these substrates under standard RCM conditions, weapplied DFT calculations to reveal that the underlying cause was a positivechange in Gibbs free energy. The change in Gibbs free energy was also foundto be positive for RCM of indole- and benzannulated terminal diolefins whenaffording smaller than 12-membered rings. We found that modification of theenediyne−diolefin substrate as the Co2(CO)6−alkyne complex allowed thetarget benzothiophene-fused 11-membered dienediyne to be obtained viaRCM; the alkyne complexation strategy therefore provides one valid technique for overcoming challenges to macrocyclization ofthis kind.

U2 - http://dx.doi.org/10.1021/acs.joc.5b00409

DO - http://dx.doi.org/10.1021/acs.joc.5b00409

M3 - Article

VL - 80

SP - 5546

EP - 5555

JO - Journal of Organic Chemistry

JF - Journal of Organic Chemistry

SN - 0022-3263

ER -