Aluminium Chloride Hexahydrate (AlCl₃ · 6H₂O): An Efficient, Facile, Mild, And Highly Chemoselective Catalytic Deprotection of Tert-Butyldimethylsilyl (TBS) Ethers

Catalyst‐Driven Scaffold Diversity: Selective Synthesis of Spirocycles, Carbazoles and Quinolines from Indolyl Ynones

“…We were unable to uncover a catalyst that could successfully initiate spirocyclisation and subsequent rearrangement on its own. However, first performing the spirocyclisation using 2 mol % of AgOTf as catalyst in isopropanol, followed by the addition of 5 mol % of AlCl 3 ⋅6H 2 O and subsequent heating in a microwave gave quinoline 7 a in high yield (Scheme ) . Following Ag I ‐mediated spirocyclisation, it is thought that the Al III catalyst promotes enolate formation and subsequent cyclopropanation to form 12 a , which can then fragment to form 13 a and aromatise to give quinoline 7 a (either by simple proton shuttling, or by a series of 1,5‐sigmatropic H‐transfer reactions).…”

“…We next examined whether we could initiate an alternative rearrangement commencing from ynone 1a,b ys eeking to promote cyclopropanation of an enolatef rom the lesss ubstituted branch of the cyclopentenone;m ore oxophilic catalysts were chosen for this task, as it was thought that they would better promote the necessary enolate formation.W ew ere unable to uncover ac atalystthat could successfully initiate spirocyclisation and subsequent rearrangement on its own.H owever,f irst performing the spirocyclisation using 2mol %o f AgOTf as catalysti ni sopropanol, followed by the addition of 5mol %o fA lCl 3 ·6H 2 Oa nd subsequent heating in am icrowave gave quinoline 7a in high yield (Scheme 4). [10] Following Ag Imediated spirocyclisation, it is thought that the Al III catalyst promotes enolatef ormation and subsequent cyclopropanation to form 12 a,w hich can then fragment to form 13 a and aromatise to give quinoline 7a (either by simple proton shuttling, or by aseries of 1,5-sigmatropic H-transfer reactions).…”

1-Methyl-1,4-cyclohexadiene as a Traceless Reducing Agent for the Synthesis of Catechols and Hydroquinones

“…Hydroquinone (4b). 41 It was obtained in 15 h; eluent: hexane/ ethyl acetate 7:3, 18.2 mg, yield = 92%. 1 H NMR (CDCl 3 , 300 MHz): δ 6.72 (s, 4H), 4.39 (br s, 2OH).…”

KHF2: A Mild and Selective Desilylating Agent for Phenol tert-­Butyldimethylsilyl (TBDMS) Ethers

“…20 In the context of deprotecting alkyl silyl ethers in the presence of phenolic silyl ethers, catalytic AlCl 3 ·6H 2 O in MeOH or iPrOH has been investigated for removal of phenolic TBDMS groups. 21 Catalytic NaAuCl 4 ·2H 2 O in MeOH has been used to deprotect four phenolic TBDMS groups, but the method gave a low yield with an electron deficient phenol. 22 …”

“…20 In the context of deprotecting alkyl silyl ethers in the presence of phenolic silyl ethers, catalytic AlCl 3 •6H 2 O in MeOH or i-PrOH has been investigated for removal of phenolic TBDMS groups. 21 Catalytic NaAuCl 4 •2H 2 O in MeOH has been used to deprotect four phenolic TBDMS groups, but the method gave a low yield with an electron-deficient phenol. 22 In connection with ongoing work on desilylations of some nucleoside substrates, we found the compounds to be exceptionally sensitive to a variety of conventional fluoride reagents.…”