Annulation Of Salicylaldehydes Research Articles

NaHCO3‐promoted Formal [4+3] Annulation of Salicylaldehydes with Isoquinolinium Salts Accessing Isoquinoline‐fused Benzo[f][1,3]oxazepines

A concise and practical sustainable strategy for modular access to isoquinoline‐fused benzo[f][1,3]oxazepine derivatives through a formal [4+3] annulation of commercially available salicyaldehydes with isoquinolinium salts has been developed. The reactions proceeded through the formation of two new bonds (C=C and C‐O) and a seven‐membered heterocyclic ring in one pot. Remarkably, use of simple NaHCO3 as a mild base, open atmosphere, nonhazardous reagents, nice functional group tolerance, and easily scale up are added characteristics to this approach. A wide range of substrates are compatible with this mild reaction system, thereby proving a facile and reliable protocol for constructing a benzo[f][1,3]oxazepine skeletons.

Ru(II)-Catalyzed Decarbonylative Alkylation and Annulations of Benzaldehydes with Iodonium Ylides under Chelation Assistance.

A Ru(II)-catalyzed decarbonylative alkylation and annulation of salicylaldehydes and 2-aminobenzaldehydes with iodonium ylides has been developed for the synthesis of dibenzo[b,d]furans and NH-free carbazolones. The reaction proceeds smoothly under mild conditions with a low catalyst loading and a broad substrate compatibility. Notably, hydroxy and free amino groups were demonstrated to be the effective directing groups, enabling the successful aldehyde C-H bond activation and subsequent decarbonylation and annulation under the inexpensive Ru(II) catalyst.

Efficient Synthesis of 3-Sulfonyl-2-sulfonylmethyl-2H-chromenes via Tandem Knoevenagel Condensation/Oxa-Michael Addition Protocol

An organocatalytic [4 + 2] cascade annulation of salicylaldehydes and 1,3-bisarylsulfonylpropenes has been developed. This protocol enables the efficient and straightforward synthesis of a new series of 3-sulfonyl-2-sulfonylmethyl-2H-chromenes that are useful for exploring pharmacologically valued compounds. Further reductive modifications result in 3-desulfonylated chromene or chromane derivatives. This protocol can be expanded to the synthesis of 3-sulfonyl-2-sulfonylmethyl 1,2-dihydroquinoline.

NHC/Copper-Cocatalyzed [4 + 3] Annulations of Salicylaldehydes with Aziridines for the Synthesis of 1,4-Benzoxazepinones.

N-heterocyclic carbene/copper-cocatalyzed [4 + 3] annulation of salicylaldehydes with aziridines was developed, giving the corresponding 1,4-benzoxazepinones in good yields with exclusive regioselectivity. Copper serves as a Lewis acid to activate the small strained aziridines, and the formation of NHC-salicylaldehyde adduct plays an important role in improving the regioselectivity.

One-pot synthesis of benzopyrano[2,3-d]pyrimidine derivatives catalyzed by LDHs@Propyl-ANDSA

A general, effective, and operationally simple approach to highly substituted benzopyrano[2,3-d]pyrimidine through the annulation of salicylaldehydes, malononitrile, and secondary amines is explained. The reaction is promoted by the Brønsted–Lowry acid, furnishing a variety of benzopyrano[2,3-d]pyrimidine derivatives in synthetically useful yields.

Palladium(0)-catalyzed [4+2] Annulation of Salicylaldehydes and Propargyl Carbonates to Produce 3,4-Dihydro-2-methylene-2H-1-benzopyran-4-ols

Palladium(0)-catalyzed synthesis of 3,4-dihydro-2-methylene-2H-1-benzopyran-4-ols via annulation between salicylaldehyde and propargyl carbonate using a formate reductant is reported herein. The an...

On-Water Cp*Ir(III)-Catalyzed C-H Functionalization for the Synthesis of Chromones through Annulation of Salicylaldehydes with Diazo-Ketones.

A high-valent Ir(III)-catalyzed C-H bond functionalization is carried out for the first time on water for the synthesis of a biologically relevant chromone moiety. The C-H activation and annulation of salicylaldehydes with diazo-compounds provided the desired chromones. The synthesis of C3-substitution-free chromones has also been demonstrated by a one-pot decarboxylation by employing tert-butyl diazoester. C3 and C5 C-H activations of the product chromone are also carried out under different conditions for further diversification.

Cobalt-Catalyzed Annulation of Salicylaldehydes and Alkynes to Form Chromones and 4-Chromanones.

A unique cobalt(I)-diphosphine catalytic system has been identified for the coupling of salicylaldehyde (SA) and an internal alkyne affording a dehydrogenative annulation product (chromone) or a reductive annulation product (4-chromanone) depending on the alkyne substituents. Distinct from related rhodium(I)- and rhodium(III)-catalyzed reactions of SA and alkynes, these annulation reactions feature aldehyde C-H oxidative addition of SA and subsequent hydrometalation of the C=O bond of another SA molecule as common key steps. The reductive annulation to 4-chromanones also involves the action of Zn as a stoichiometric reductant. In addition to these mechanistic features, the Co(I) catalysis described herein is complementary to the Rh(I) - and Rh(III) -catalyzed reactions of SA and internal alkynes, particularly in the context of chromone synthesis.

Cobalt‐Catalyzed Annulation of Salicylaldehydes and Alkynes to Form Chromones and 4‐Chromanones

AbstractA unique cobalt(I)–diphosphine catalytic system has been identified for the coupling of salicylaldehyde (SA) and an internal alkyne affording a dehydrogenative annulation product (chromone) or a reductive annulation product (4‐chromanone) depending on the alkyne substituents. Distinct from related rhodium(I)‐ and rhodium(III)‐catalyzed reactions of SA and alkynes, these annulation reactions feature aldehyde C−H oxidative addition of SA and subsequent hydrometalation of the C=O bond of another SA molecule as common key steps. The reductive annulation to 4‐chromanones also involves the action of Zn as a stoichiometric reductant. In addition to these mechanistic features, the CoI catalysis described herein is complementary to the RhI‐ and RhIII‐catalyzed reactions of SA and internal alkynes, particularly in the context of chromone synthesis.

Ru(ii)-Catalyzed C-H activation and annulation of salicylaldehydes with monosubstituted and disubstituted alkynes.

The Ru(ii)-catalyzed C-H activation and annulation reaction of salicylaldehydes and disubstituted alkynes affords chromones in high yields. This reaction also works with terminal alkynes and tolerates a wide range of sensitive functional groups. The selectivity pattern of this Ru(ii)-catalyzed annulation reaction is different from the known Au(i), Rh(iii)-catalyzed annulation reactions of salicylaldehydes and terminal alkynes.

Rapid syntheses of (±)-pterocarpans and isoflavones via the gold-catalyzed annulation of aldehydes and alkynes

(±)-Pterocarpan and analogues ( 4a– c) have been synthesized efficiently via the annulation of salicylaldehydes ( 1a, 1b and 1c) and o-methoxymethoxylphenylacetylene ( 2a), followed by a one-pot reduction and acidic cyclization of the ketones ( 3a– c). In addition, isoflavone derivatives ( 5a– c) have been synthesized rapidly, in two steps, via the annulation of salicylaldehyde ( 1a) and arylacetylenes ( 2b, 2c and 2d), followed by IBX/DMSO oxidation of the isoflavanones ( 3d, 3e and 3f).