Sesquiterpene lactones: total synthesis of (.+-.)-vernolepin and (.+-.)-vernomenin

Facile and Regioselective Dealkylation of Alkyl Aryl Ethers Using Niobium(V) Pentachloride

“…The 13 C NMR spectrum after 16 h also supported the formation of asymmetrical niobium salt B, in which six nonequivalent signals observed at 111.9-151.3 ppm were assigned to be the benzene ring. The niobium salt B was stable under the reaction conditions, and no significant change was observed in either the 1 H or 13 C NMR spectrum even after 24 h at 55°C. On the other hand, treatment of C with NbCl 5 in CDCl 3 at room temperature for 30 min gave a new peak at δ = 4.32 ppm.…”

“…The removal of alkyl groups from alkyl aryl ethers is one of the most fundamental reactions in organic synthesis, and strong Lewis acids (BBr 3 [13,14] and TMSI [15,16] ) and nucleophiles (EtSNa [17,18] and NaN(TMS) 2 [19] ) have been used as promoters. We anticipate that NbCl 5 may also promote C-O bond cleavage due to its strong Lewis acidity.…”

A New Synthesis of a Stereoisomeric Mixture of 3,7-Dimethylpentadec-2-yl Acetate, the Sex Pheromone of the Pine Sawflies

“…Elution with n-hexane-ether gave 17. (8) Acetic anhydride (41.1 ml) was added to a solution of 7 (17.6 g) in dry pyridine (123.4 ml) and the mixture was left to stand overnight at room temperature. Then it was poured into ice-water and extracted with 1-Benzyloxy-3, 7 -dimet hyl-6-pentadecene (9) A solution of n-heptylmagnesium bromide was prepared from n-heptyl bromide (3.58 g), magnesium (0.49 g) and dry ether (8.5 ml).…”

“…Then it was reacted with N-bromosuccinimide to give a bromohydrin (5), which smoothly yielded an epoxide (6) by treatment with potassium hydroxide. 5 ) Pyrolysis of 6 gave an allylic alcohol (7).6) The corresponding acetate (8) was treated with n-heptylmagnesium bromide in the presence of cuprous iodide to effect the chain elongation yielding the benzyl ether (9) in 93 % yield. Catalytic hydrogenation of 9 over palladium-charcoal afforded a primary alcohol (10).…”

An Uncommon Derivative of 4H-Thiopyran-4-one: 4H,8H-Thiopyrano[3,2-b]thiopyran-4,8-dione: Synthesis, Redox Properties, and Calculations

“…[23] Therefore, we encourage other groups to approach (alkyl-)substiMuch to our surprise 11 resisted deacetalization with a variety of reagents [2  HCl in THF [17] , p-toluenesulfonic tuted 3a and 3b by adoption of the disclosed route. acid in acetone [18] , H 2 SO 4 (15%) on silica gel in dichloroPhysical Properties of Compounds with a Thiopyranomethane [19] , LiBF 4 in wet acetonitrile [20] ].…”