TY - JOUR

T1 - Cr(II)-promoted internal cyclization of acyclic enediynes fused to benzo[b]thiophene core

T2 - Macrocycles versus 2-methylenecycloalkan-1-ols formation

AU - Kulyashova, A. E.

AU - Ponomarev, A. V.

AU - Selivanov, S. I.

AU - Khlebnikov, A. F.

AU - Popik, V. V.

AU - Balova, I. A.

PY - 2019/2

Y1 - 2019/2

N2 - The utility of the intramolecular Nozaki-type coupling for the synthesis of macrocyclic benzo[b]thiophene-fused enediynes has been explored. The starting acyclic enediynes were prepared by the iodocyclization of 2-(buta-1,3-diynyl)thioanisoles followed by the Sonogashira cross-coupling of the resulting iodo-substituted benzo[b]thiophene with corresponding acetylenes. We found that Cr(II)-promoted intramolecular cyclization of 7-[2-(iodoethynyl)benzo[b]thiophen-3-yl]hept-6-ynal and 7-[3-(iodoethynyl)benzo-[b]thiophen-2-yl]hept-6-ynal resulted in the formation of 11-membered macrocyclic enediynes, while both expected 10-membered enediynes cannot be produced under the Nozaki-type reaction from corresponding 6-[3-(iodoethynyl)benzo[b]thiophen-2-yl]hex-5-ynal and 6-[2-(iodoethynyl)benzo[b]thiophen-3-yl]hex-5-ynal. In the case the reaction was catalyzed by Ni(II), the attack on a proximal triple bond led to the formation of 2-methylenecycloalkane-1-ol fragments, instead of macrocyclization. The DFT analysis of the ring strain in the benzo[b]thiophene-fused 10- and 11-membered enediyne-containing cycle provides the plausible explanation of the observed regioselectivity.

AB - The utility of the intramolecular Nozaki-type coupling for the synthesis of macrocyclic benzo[b]thiophene-fused enediynes has been explored. The starting acyclic enediynes were prepared by the iodocyclization of 2-(buta-1,3-diynyl)thioanisoles followed by the Sonogashira cross-coupling of the resulting iodo-substituted benzo[b]thiophene with corresponding acetylenes. We found that Cr(II)-promoted intramolecular cyclization of 7-[2-(iodoethynyl)benzo[b]thiophen-3-yl]hept-6-ynal and 7-[3-(iodoethynyl)benzo-[b]thiophen-2-yl]hept-6-ynal resulted in the formation of 11-membered macrocyclic enediynes, while both expected 10-membered enediynes cannot be produced under the Nozaki-type reaction from corresponding 6-[3-(iodoethynyl)benzo[b]thiophen-2-yl]hex-5-ynal and 6-[2-(iodoethynyl)benzo[b]thiophen-3-yl]hex-5-ynal. In the case the reaction was catalyzed by Ni(II), the attack on a proximal triple bond led to the formation of 2-methylenecycloalkane-1-ol fragments, instead of macrocyclization. The DFT analysis of the ring strain in the benzo[b]thiophene-fused 10- and 11-membered enediyne-containing cycle provides the plausible explanation of the observed regioselectivity.

KW - Allylic alcohols

KW - Benzothiophene

KW - Diacetylenes

KW - Enediynes

KW - Intramolecular Nozaki‐Hiyama‐Kishi reactions

KW - Iodocyclization

KW - ANTITUMOR ANTIBIOTICS

KW - ELECTROPHILIC CYCLIZATION

KW - DYNEMICIN-A

KW - Intramolecular Nozaki-Hiyama-Kishi reactions

KW - 10-MEMBERED RING

KW - DEPENDENT BERGMAN CYCLIZATION

KW - NUCLEOPHILIC ACTIVATION

KW - DESIGNED ENEDIYNES

KW - COUPLING REACTION

KW - METHYL THIOGLYCOLATE

KW - HIYAMA-KISHI REACTIONS

UR - http://www.scopus.com/inward/record.url?scp=85048578525&partnerID=8YFLogxK

UR - http://www.mendeley.com/research/criipromoted-internal-cyclization-acyclic-enediynes-fused-benzobthiophene-core-macrocycles-versus-2m

U2 - 10.1016/j.arabjc.2018.05.005

DO - 10.1016/j.arabjc.2018.05.005

M3 - Article

AN - SCOPUS:85048578525

VL - 12

SP - 151

EP - 167

JO - Arabian Journal of Chemistry

JF - Arabian Journal of Chemistry

SN - 1878-5352

IS - 2

ER -