Gold(I)‐, Palladium(II)‐, Platinum(II)‐, and Mercury(II)‐Catalysed Spirocyclization of 1,3‐Enynediols: Reaction Scope

Abstract

The spirocyclization of different 1,3‐enynediols was investigated. The reaction was only efficient for the synthesis of [5,6]‐spiroacetals. In this case, the reaction was characterized by almost quantitative yields, short reaction times, and low catalyst loadings (0.5–1 %). When the synthesis of [6,6]‐spiroacetals was attempted, the reaction suffered from poor regioselectivity and a higher propensity of the intermediate dienol ethers to decompose under the acidic conditions, and it became no longer viable. But it is possible to generate the dienol ethers cleanly under milder conditions as a mixture of regioisomers. This striking difference in reaction efficiency was explained by the unstable dienol ethers cyclizing more quickly to give [5,6]‐spiroacetals than to give [6,6]‐spiroacetals. In this study, the successful application of a new cationic palladium pincer complex for electrophilic alkyne activation at room temperature has been demonstrated for the first time.

[3,3]-Acyloxy Rearrangement-Triggered Regioselective Hydration of δ-Acetoxy-α,β-Alkynoates/Halo Alkynes

“…To a stirred solution of but-3-yn-1-ol (350 mg, 6.25 mmol) in acetone, silver nitrate (1.06 g, 6.25 mmol) and NBS (1.67 g, 1.5 mmol) were added at room temperature under an inert atmosphere and stirred for 6 h. After completion of the reaction (monitoring by TLC), hexane was added and filtered through a pad of Celite. The organic solvent was evaporated under reduce pressure, and crude was protected by following the procedure P-3 to yield 3k (800 mg, 67% yield over two steps) as a yellow-colored liquid; The analytical data are in complete agreement with those reported in the literature …”

Synthesis of Trifluoromethylated Sultones from Alkenols Using a Copper Photoredox Catalyst

“…High-resolution mass spectra were measured using electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI) with a quadrupole time-of-flight (Q-TOF) detector. The following compounds were synthesized according to the reported procedures, and the spectroscopical data are consistent with those reported: 2-methylhex-5-en-2-ol 3e , 2,2-diphenylpent-4-en-1-ol 3f , diethyl-2-allyl-2-(hydroxymethyl)­malonate 3g , (1-allylcyclohexyl)­methanol 3h , rel -(1 R ,6 S )-7-oxabicyclo­[4.1.0]­heptane, rel -(1 S ,2 R )-2-allylcyclohexan-1-ol 3i , 1-phenylpent-4-en-1-ol 3k , pent-4-en-1-yl trifluoromethanesulfonate 12 , 2-(chloromethyl)­tetrahydrofuran, and 5-methoxypent-1-ene 14 …”

Reactions of Titanium Imides and Hydrazides with Boranes

“…Among the latter set there are electron-poor (HBAr F 2 ), dialkyl (9-BBN), and electron-rich (HBPin) homologues. Among other boranes assessed were HBCy 2 , HBMes 2 , HB­(NAr′CH) 2 , HB­(N i PrCH 2 ) 2 , and HBCat (Cat = 1,2-O 2 C 6 H 4 ). These either gave nonisolable equilibrium mixtures, poorly defined products, or no reaction at all.…”

“…Cp*Ti­{MeC­(N i Pr) 2 }­(NR) (R = t Bu or Tol ( 10 )), Cp*Ti­{MeC­(N i Pr) 2 }­(NO t Bu), , Cp*Ti­{MeC­(N i Pr) 2 }­(NNR 2 ) (R 2 = Me 2 ( 2 ), Ph 2 ( 18 ) or CPh 2 ( 4 )), , HBCy 2 , H 2 BTex, HBAr F 2 , , HBMes 2 , HB­(NAr′CH) 2 , HB­(N i PrCH 2 ) 2 were synthesized according to literature procedures. Other boranes were obtained from commercial source and used without additional purification.…”