Oxygen heterocycles by the Parham cyclialkylation

Abstract

The addition of butyllithium at -100 °C to -bromoalkyl ethers of o-bromophenol (and its congeners) led to preferential exchange of the aryl bromine at position 2. The resulting organolithium reagents, under suitable conditions, cyclized to afford 2,3-dihydrobenzofurans (6), 3,4-dihydro-2/f-l-benzopyrans (13), or 2,3,4,5-tetrahydro-l-benzoxepins (16) in good yields, but less satisfactory results were obtained with the intermediate expected to produce 8-methyl-3,4,5,6-tetrahydro-2ff-l-benzoxocin (19). -Bromoethyl and -bromopropyl ethers of suitable dibromophenols were treated successively with 2 equiv of butyllithium and an electrophile to yield derivatives of 6 and 13.

Probing of the Ligand Anatomy: Effects of the Chelating Alkoxy Ligand Modifications on the Structure and Catalytic Activity of Ruthenium Carbene Complexes

“…(Scheme 4). [21] Wittig olefination of aldehydes 8E and 8F led to the formation of corresponding styrenes 7E and 7F. [22] The previously optimised [7,8] exchange reaction [22] of 7A, 7B, 7C with Grubbss carbene 2b in the presence of CuCl used as a phosphine scavenger, followed by routine flash chromatography led to the formation of the "RO-modified" carbenes 6A-C as an air-stable green microcrystalline solids (34-48 % yield, Scheme 5).…”

Silver‐Catalyzed Carbocyclization of Azide‐Tethered Alkynes: Expeditious Synthesis of Polysubstituted Quinolines

“…Parham cyclialkylation of 3 q occurred smoothly to form dihydrofuroquinoline 11 in 92% yield. [21] The bromated quinoline 3 r could be converted to azide 12 in 98% yield when treated with sodium azide, [22] which could be used for further modifications. Notably, the tetracyclic products 13 [23] and 14 [24] were obtained in 85% and 51% yields, respectively, via corresponding coupling reactions.…”

Determination of the relationship between theoretical vibrational frequencies and experimental IR absorbance bands in organic molecules: computational study of oxane, chromane and flavan

“…The classic synthetic pathway of chromane from the cyclization of 3‐( o ‐bromophenoxy)propyl bromide at −78 0 C and −100 0 C using butyllithium as transmetallating base agent is simplified by following a standard hydrogenation procedure of commercially available 4‐chromanone in ethanol over Pd(OH) 2 /C to give the product, chromane in 87% yield. The 1 H NMR methylene resonance at δ 2.86 (t, 2 H, J 6 Hz and 7 Hz, 2 x H‐4) proved that the carbonyl was replaced by CH 2 .…”