Synthesis of functionalized benzopyrans by sequential [3+3]-cyclization—Williamson reactions of 1,3-bis(trimethylsilyloxy)-7-chlorohepta-1,3-dienes

Functionalized benzopyrans were regioselectively prepared by [3+3]-cyclization of 1,3-bis(trimethylsilyloxy)-7-chlorohepta-1,3-dienes with 3-silyloxy-2-eno-1-ones and subsequent intramolecular Williamson reactions of the salicylates thus formed.     

Synthesis of 5-(2-aryl-2-haloethyl)salicylates by the first domino ‘[3+3] cyclization/ring-cleavage’ reactions of 1,3-bis(silyloxy)-1,3-butadienes with 3-acetyl-5-aryl-4,5-dihydrofurans

5-(2-Aryl-2-haloethyl)salicylates are efficiently prepared by the first domino ‘[3+3] cyclization/ring-cleavage’ reactions of 1,3-bis(silyloxy)-1,3-butadienes with 3-acetyl-5-aryl-4,5-dihydrofurans.     

Regioselective synthesis of 6-aryl-5-(chloroethyl)salicylates by domino ‘[3+3] cyclization/homo-Michael’ reactions of 1,3-bis(silyloxy)-1,3-butadienes with 1-formyl- and 1-acetyl-1-aroyl-cyclopropanes

Functionalized 3-aryl-4-(chloroethyl)phenols are regioselectively prepared by domino ‘[3+3] cyclization/homo-Michael’ reactions of 1,3-bis(silyloxy)-1,3-butadienes with 1-formyl- and 1-acetyl-1-aroyl-cyclopropanes.     

Regioselective synthesis of diaryl sulfides by [3+3] cyclizations of 1,3-bis(trimethylsilyloxy)-1,3-dienes

Functionalized and sterically encumbered diaryl sulfides were prepared based on [3+3] cyclizations of 1,3-bis(trimethylsilyloxy)-1,3-dienes.     

Regioselective synthesis of sterically encumbered diaryl ethers based on one-pot cyclizations of 4-aryloxy-1,3-bis(trimethylsilyloxy)-1,3-dienes

Sterically encumbered diaryl ethers are prepared based on formal [3+3] cyclizations of novel 4-aryloxy-1,3-bis(trimethylsilyloxy)-1,3-dienes.     

Synthesis of 1-azaxanthones by condensation of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with 3-(cyano)benzopyrylium triflates and subsequent domino ‘retro-Michael/nitrile-addition/heterocyclization’ reaction

Functionalized 1-azaxanthones (5-oxo-5H-[1]-benzopyrano[2,3-b]pyridines) were prepared by TMSOTf-mediated condensation of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with 3-cyanochromones and subsequent base-mediated domino ‘retro-Michael/nitrile-addition/heterocyclization’ reaction.     

Regioselective synthesis of amino- and nitroarenes based on [3+3] cyclocondensations of 1,3-bis(silyloxy)-1,3-butadienes

Functionalized amino- and nitro-substituted biaryls and dibenzo[b,d]pyrid-6-ones (6(5H)-phenanthridinones) were prepared by [3+3]cyclocondensation of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with nitro-substituted 1-aryl-1-silyloxy-1-en-3-ones and subsequent hydrogenation. 4-Nitro- and 4-aminophenols were prepared based on formal [3+3] cyclizations of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with 3-ethoxy-2-nitro-2-en-1-ones.     

Synthesis of functionalized triarylmethanes by combination of FeCl3-catalyzed benzylations of acetylacetone with [3+3] cyclocondensations

Functionalized triarylmethanes are prepared in two steps by FeCl₃-catalyzed benzylation of acetylacetone to give 3-(diarylmethyl)pentane-2,4-diones and subsequent formal [3+3] cyclization of the latter with 1,3-bis(trimethylsilyloxy)-1,3-dienes.     

Regioselective synthesis of functionalized 2-(phenylthio)benzoates by ‘[3+3] cyclization/homo-Michael’ reactions of 1-methoxy-1-trimethylsilyloxy-3-phenylthio-1,3-butadienes with 1,1-diacylcyclopropanes

2-(Phenylthio)benzoates containing a remote halide function are regioselectively prepared by ‘[3+3] cyclization/homo-Michael’ reactions of 1-methoxy-1-trimethylsilyloxy-3-phenylthio-1,3-butadienes with 1,1-diacylcyclopropanes.     

Chelation control in the [3+3] annulation reaction of alkoxy-substituted 1,1-diacylcyclopropanes with 1,3-bis(trimethylsilyloxy)-1,3-butadienes

Functionalized arenes were prepared by chelation-controlled ‘[3+3] cyclization/homo-Michael’ reactions of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with benzyloxy- or methoxy-substituted 1,1-diacylcyclopropanes.     

Synthesis of functionalized triarylmethanes based on a ‘FeCl3-catalyzed benzylation/[3+3] cyclocondensation’ strategy

Functionalized triarylmethanes are prepared in two steps by FeCl₃-catalyzed benzylation of acetylacetone to give 3-(diarylmethyl)pentane-2,4-diones and subsequent formal [3+3] cyclization of the latter with 1,3-bis(trimethylsilyloxy)-1,3-dienes.     

Regioselective synthesis of spiro-cyclopropanated 1-aminopyrrol-2-ones by Bi(OTf)3-catalyzed one-pot ‘Mukaiyama-Michael addition/cyclization/ring-contraction’ reactions of 1,2-bis(trimethylsilyloxy)cyclobutene with 1,2-diaza-1,3-butadienes

Unknown spiro-cyclopropanated 1-aminopyrrol-2-ones are regioselectively prepared in high yields by Bi(OTf)₃-catalyzed one-pot ‘Mukaiyama-Michael addition/cyclization/ring-contraction’ reactions of 1,2-bis(trimethylsilyloxy)cyclobutene with 1,2-diaza-1,3-butadienes at room temperature.     

Domino reaction of 1,3-bis(trimethylsilyloxy)-1,3-dienes with oxalyl chloride: general and stereoselective synthesis of gamma-alkylidenebutenolides

The Lewis acid catalyzed cyclization of oxalyl chloride with 1,3-bis(trimethylsilyloxy)-1,3-dienes 3, derived from 1,3-dicarbonyl compounds 1, provides a new and general approach for the synthesis of gamma-alkylidenebutenolides 4, a pharmacologically and synthetically important class of substances. A variety of butenolides were efficiently prepared in good yields and with very good regio- and stereoselectivities. An up-scaling of the reaction was possible. The use of the Lewis acid trimethylsilyl-trifluoromethanesulfonate (TMSOTf) proved to be superior to other activation conditions. Sterically undemanding gamma-alkylidenebutenolides could be prepared alternatively by reaction of the corresponding 1,3-dicarbonyl dianions with N,N'-dimethoxy-N,N'-dimethylethanediamide (2d). In contrast to the dianion method, the Lewis acid catalyzed reaction also facilitated the cyclization of sterically hindered, base-labile, cyclic and functionalized substrates. From a methodology viewpoint, the dianion reaction represents the first cyclization of a bis-Weinreb amide and the first cyclization of an oxalic acid-synthon with an ambident dianion. The TMSOTf-catalyzed reactions are both the first cyclizations of 1,3bis(trimethylsilyloxy)-1,3-dienes with a C2 dielectrophile and the first cyclizations of 1,3-bis(trimethylsilyloxy)-1,3-dienes with a carboxylic acid dichloride or a related dielectrophile.     

Synthesis of of sterically encumbered biaryls based on a ‘copper(I)-catalyzed arylation/[3+3] cyclocondensation’ strategy

Sterically encumbered biaryls are prepared in two steps by combination of the CuI-proline-catalyzed arylation of acetylacetone with formal [3+3] cyclizations of 1,3-bis(trimethylsilyloxy)-1,3-dienes. In addition, the synthesis of 4,6- and 5,6-diarylsalicylates based on [3+3] cyclizations is reported.     

Synthesis of sterically encumbered biaryls based on a ‘copper(I)-catalyzed arylation/[3+3] cyclocondensation’ strategy

Sterically encumbered biaryls are prepared in two steps by CuI-proline-catalyzed arylation of acetylacetone to give 3-arylpentane-2,4-diones and subsequent formal [3+3] cyclization of the latter with 1,3-bis(trimethylsilyloxy)-1,3-dienes.     

Synthesis of 7-hydroxy-6H-benzo[c]chromen-6-ones based on a ‘[3+3] cyclization/domino retro-Michael-aldol-lactonization’ strategy

The TiCl₄-mediated [3+3] cyclization of 2,4-bis(trimethylsilyloxy)penta-1,3-diene with 3-silyloxyalk-2-en-1-ones afforded 2-acetylphenols, which were transformed into functionalized chromones. The Me₃SiOTf-mediated condensation of the latter with 1,3-bis(silyl enol ethers) and subsequent domino ‘retro-Michael-aldol-lactonization’ reaction afforded 7-hydroxy-6H-benzo[c]chromen-6-ones.     

Synthesis of 7-hydroxy-2-(2-hydroxybenzoyl)benzo[c]chromen-6-ones by sequential application of domino reactions of 1,3-bis(silyl enol ethers) with benzopyrylium triflates

The domino, Michael-retro-Michael-aldol, reaction of 2,4-bis(trimethylsilyloxy)penta-1,3-diene with 3-formylchromones afforded 4-(2-hydroxybenzoyl)-2-acetylphenols, which were transformed into 6-(2-hydroxybenzoyl)chromones. The Me₃SiOTf-mediated condensation of the latter with 1,3-bis(silyl enol ethers) and subsequent domino ‘retro-Michael-aldol-lactonization’ reaction afforded 7-hydroxy-2-(2-hydroxybenzoyl)benzo[c]chromen-6-ones.     

Regioselective synthesis of functionalized 4-nitro- and 4-amino-phenols based on formal [3+3] cyclocondensations of 3-ethoxy-2-nitro-2-en-1-ones with 1,3-bis(silyloxy)-1,3-butadienes

Functionalized 4-nitro- and 4-aminophenols were regioselectively prepared based on [3+3] cyclizations of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with 3-ethoxy-2-nitro-2-en-1-ones.     

Synthesis of dibenzo[b,d]pyran-6-ones based on [3 + 3] cyclizations of 1,3-bis(silyl enol ethers) with 3-silyloxy-2-en-1-ones

Functionalized dibenzo[b,d]pyran-6-ones were prepared by formal [3 + 3] cyclization of 1,3-bis(silyl enol ethers) with 3-silyloxy-2-en-1-ones or 1,1-diacetylcyclopropane to give functionalized salicylates, Suzuki cross-coupling reactions of the corresponding triflates, and subsequent BBr3-mediated lactonization. A second approach to dibenzo[b,d]pyran-6-ones relies on the [3 + 3] cyclization of 1,3-bis(silyl enol ethers) with 1-(2-methoxyphenyl)-1-(trimethylsilyloxy)alk-1-en-3-ones and subsequent BBr3-mediated lactonization.     

Synthesis of functionalized diaryl selenides by the first [3+3] cyclocondensations of 1,3-bis(silyloxy)-1,3-butadienes with organoselenium compounds

Functionalized diaryl selenides were prepared by the first [3+3] cyclizations of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with organoselenium compounds (i.e., 2-(phenylselanyl)-3-silyloxy-3-en-1-ones).