Microwave structure determination for the furan-hydrogen chloride complex

Abstract

H-3, at 4.64 (br dd, J = 3.0, 1.5 Hz),15 as the equatorial orientation, indicating the right stereochemistry for maytansinol (2).Similarly, treatment of the epoxy aldehyde 20 with lithium enolate of EtOAc (5 equiv in THF, -78 °C, 30 min) now produced the adduct as almost all single isomer 27a (Scheme IV). Its hydroxy group was protected with Me2-Z-BuSiCI [5 equiv and imidazole (12 equiv) in DMF, 35 °C, 12 h], and then the carboxylic ester 27b was hydrolyzed with a mixture of 3 N 1:5:2 KOH-EtOH-THF (45 °C, 7 h) to 27c (52% overall yield from 20). Cyclization of the acid 27c was achieved with mesitylenesulfonyl chloride21" (20 equiv ¡-Pr2EtN (20 equiv and n-Bu4NOH in benzene, 40 °C) to afford 28a [ NMR 1.00 (Me-6, d, J =

Competition between H···π and H···O Interactions in Furan Heterodimers

“…The Fu–HCl and Fu–HCN complexes show C 2 v symmetry with both basis sets. It is worth noticing the excellent agreement between our calculated structure of Fu–HCl and the Fu–HCl dimer identified by Shea and Kukolich , using microwave spectroscopy. Our calculated H···O bond length is 1.93 (1.97) Å (MP2/aVTZ (MP2/VTZ) levels of theory) which compares very well to the experimental value of 1.97 Å.…”

The microwave spectrum and structure of the pyridine–CO complex

“…The last complex was between HCl and furan where HCl formed a hydrogen bond to oxygen in furan in its plane. 8,9 We report here the first observation of the pyridine-CO complex through its microwave spectrum. Rather unexpectedly, CO was found not to bind above the plane to the aromatic system of pyridine, but in the molecular plane of pyridine and not simply along its C 2 axis.…”