Reaction of Benzyl Grignard Reagents with Trifluoroacetyldihydropyrans and Other Cyclic β-Alkoxy-α,β-Unsaturated Trifluoromethylketones

Highly Chemoselective Synthesis of 6‐Alkoxy‐1‐alkyl(aryl)‐3‐trifluoroacetyl‐1,4,5,6‐tetrahydropyridines and 1‐Alkyl(aryl)‐6‐amino‐3‐trifluoroacetyl‐1,4,5,6‐tetrahydropyridines

“…In a review of the literature, only four references were found. Three of them report Grignard reactions carried out with 6-alkoxy-3-trifluoroacetyl-4,5-dihydro-6H-pyrans 1 and 2 to obtain different compounds, depending on the nature of the Grignard reagent and the reaction conditions [27] and one reference reports the reactions of compounds 1 and 2 with hydroxylamine hydrochloride to selectively give fluorine-containing 4H-pyrano[3,2-d]isoxazoles or 4-(cyanoethyl)dihydroisoxazole in moderate to high yields. [28] The use of cyclic enones such as 3-trihaloacetyl-4,5-dihydrofuran and 3-trihaloacetyl-5,6-dihydro-4H-pyran has been attracting much attention because these compounds can easily react with nucleophiles, generating new aliphatic or heterocyclic systems by a process that involves the opening of the furan or pyran ring by the nucleophile and the subsequent closure of the alkyl-hydroxy side chain.…”

Preparation of new 2‐amino‐ and 2,3‐diamino‐pyridine trifluoroacetyl enamine derivatives and their application to the synthesis of trifluoromethyl‐containing 3H‐pyrido[2,3‐b][1,4] diazepinols

“…The presence of trifluoromethyl groups directly linked to acyclic and cyclic organic compounds confers special chemical, physical and biological properties to molecules, mostly due to the elevated electronegative and lipophilic character of fluorine atoms [1][2][3][4][5][6][7][8][9][10][11]. Thus, much attention has been given to the synthesis of trifluorinated compounds, many of which have been shown to be of notable pharmacologic value [12][13].…”

Palladium-Catalyzed Intramolecular C-H Activation: A Synthetic Approach towards Polycyclic Aromatic Hydrocarbons

“…16 The o-bromoaromatic aldehydes 2a-f were in turn prepared in excellent yield by the Vilsmeier-Haack-type reaction from the corresponding tetralone derivatives 17 followed by the aromatization with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ). Table 1 Optimization Studies a Entry Catalyst Base Solvent Temp (°C) Yield (%) b 1 Pd(OAc) 2 Cs…”

“…16 The o-bromoaromatic aldehydes 2a-f were in turn prepared in excellent yield by the Vilsmeier-Haack-type reaction from the corresponding tetralone derivatives 17 followed by the aromatization with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ). After a thorough screening of different combinations of reagent, solvent, and temperature, the optimized reaction conditions were found when substrate 3a (1 mmol), Pd(PPh 3 ) 2 Cl 2 (5 mol%), and NaOAc (1.5 mmol) in N,Ndimethylacetamide (DMA, 5 mL) were heated at 130-140°C for two hours to obtain the cyclized product 4.…”