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Abstract: A new palladium‐catalyzed reductive [5+1] cycloaddition of 3‐acetoxy‐1,4‐enynes with CO, enabled by hydrosilanes, has been developed for delivering valuable functionalized phenols. This methodology employs hydrosilanes as the external reagent to facilitate the [5+1] carbonylative benzannulation. The reaction is a conceptually and mechanistically novel carbonylative cycloaddition route for the construction of substituted phenols, through the formation of four new chemical bonds, with excellent functional‐group tolerance. [ABSTRACT FROM AUTHOR]

Abstract: α‐Carbonyl alkyl bromides are powerful reactive species for the formation of carbon–carbon bonds. Strategies relying on intermolecular C−H functionalization and cross‐coupling reactions, also referred to as intramolecular cyclization, have been employed for the construction of alkenes, alkanes, ketones, and other natural‐product‐like ring compounds from simple alkynes, alkenes, and 1,n‐enynes. In view of the importance of these α‐carbonyl alkyl bromides, especially the difluoro carbonyl alkyl bromides, many researchers have focused their efforts to develop facile and mild synthetic methods for compounds with important biological activities. This review aims to briefly discuss the latest developments in the transformation of α‐carbonyl alkyl bromides with emphasis on the related reaction mechanisms. [ABSTRACT FROM AUTHOR]

A new, radical-mediated, divergent bicyclization of 1,n-enynes by α-C( sp3)-H oxidative functionalization of alkyl nitriles is described using the Sc(OTf)3 and Ag2O system. The reaction allows the selective functionalization of one or two C( sp3)−H bonds α to the nitrile group by both oxidants and the substitution effect co-controlled the divergent bicyclization reactions, and offers a step- and atom-economical access to diverse polycycles with broad substrate scope and high selectivity. [ABSTRACT FROM AUTHOR]

A new visible light-initiated 1,5-hydride radical shift strategy has been developed to enable the one-step functionalization of both a C( sp3)Br bond and a C( sp3)H bond adjacent to the same carbon atom. This visible light photoredox catalysis offers a mild and straightforward access to diverse five-membered carbocyclic ring-fused polycyclic hydrocarbons with high turnover numbers (TONs; up to 4.93×103) and broad substrate scope. [ABSTRACT FROM AUTHOR]

The Cu-catalyzed oxidative [2+2+1] annulation of 1,n-enynes (n = 6, 7) with α-carbonyl alkyl bromides through C–Br/C–H functionalization has been developed. Using Ag2CO3/tert-butyl hydroperoxide (TBHP) as co-oxidants, α-carbonyl alkyl bromides provide two bonds, the α-C(sp3)–Br bonds and the α-C(sp3)–H bonds, to cyclize with the 1,n-enynes and Cu(MeCN)4PF6, thus forming three new C–C bonds and two rings in a single reaction. [ABSTRACT FROM AUTHOR]

A new metal-free method for the nitrative cyclization of 1-ethynyl-2-(vinyloxy)benzenes with tert-butyl nitrite ( t-BuONO), air and water at room temperature is presented, in which an oxygen atom is introduced into the carbon-carbon triple bond to form a new carbonyl group through dioxygen activation. [ABSTRACT FROM AUTHOR]

We here describe a new palladium-catalyzed oxidative 6-exo-trig cyclization of 1,6-enynes at room temperature using tBuONO as an oxidant for the synthesis of 3-bicyclo[4.1.0]heptan-5-ones. This cascade strategy involves the hydration, cyclization and cyclopropanation sequence, and represents a new transition-metal-catalyzed oxidative cyclization of 1,6-enynes in a 6-exo-trig fashion. [ABSTRACT FROM AUTHOR]

A new metal-free oxidative radical [2+2+1] carbocyclization of benzene-linked 1, n-enynes with two C(sp3)H bonds adjacent to the same heteroatom is described. This method achieves two C(sp3)H oxidative functionalizations and an annulation, thus providing efficient and general access to a variety of fused five-membered carbocyclic hydrocarbons. [ABSTRACT FROM AUTHOR]

A new metal-free radical 5- exo-dig cyclization of phenol-linked 1,6-enynes with O2, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), and tBuONO is described. With this general method, carbonylated benzofurans can be accessed through incorporation of two oxygen atoms into the product from O2 and TEMPO through dioxygen activation and oxidative cleavage of the NO bond, respectively. [ABSTRACT FROM AUTHOR]

Here we describe the one-pot construction of the pyrrolo[4,3,2-de]quinolinone scaffold by a cascade nitration/cyclization sequence of 1,7-enynes with tBuONO and H2O. The cascade proceeds through alkene nitration, 1,7-enyne 6- exo-trig cyclization, CH nitrations, and redox cyclization, and exhibits excellent functional group tolerance. The mechanism was investigated using in situ high-resolution mass spectrometry (HR-MS). [ABSTRACT FROM AUTHOR]

Ray of light: 10a,11‐Dihydro‐10H‐benzo[b]fluorenes were synthesized by a visible‐light‐catalyzed tandem cyclization of 1,6‐enynes with arylsulfonyl chlorides. This method extends the scope of enyne cyclizations and represents a new synthetic application of arylsulfonyl chlorides. [ABSTRACT FROM AUTHOR]

The article presents chemical equations related to the article "Copper-Catalyzed Radical [2 + 2 + 1] Annulation of Benzene-Linked 1,n-Enynes with Azide: Fused Pyrroline Compounds" by M. Hu and others, published in the "Organic Letters" in 2015.

A new metal-free radical 5-exo-dig cyclization of phenol-linked 1,6-enynes with O2, TEMPO and tBuONO is described. [ABSTRACT FROM AUTHOR]

A novel copper-catalyzed cascadecyclization of 1,7-enynes withmetal sulfides is described. This sulfur-incorporation method providesstraightforward access toward the important thiophene-fused quinolin-4(5H)-one scaffold through cyclization and double C–Sbond formation cascade, and the chemoselectivity of this 1,7-enynecyclization toward 1,3,3a,9b-tetrahydrothieno[3,4-c]quinolin-4(5H)-ones and 3,3a-dihydrothieno[3,4-c]quinolin-4(5H)-ones can be controlledby varying the sulfur resources. [ABSTRACT FROM AUTHOR]

An abstract of the article "Cascade Nitration/Cyclization of 1,7-Enynes with tBuONO and H2O: One-Pot Self-Assembly of Pyrrolo[4,3,2-de]quinolinones" is presented.

A new method for the cascade cyclization of 1,7-enynes with aromatic sulfonyl chlorides by using a low-cost and more abundant Cu catalyst is reported. [ABSTRACT FROM AUTHOR]