Diynes and Aldehydes

Scheme 5.18 [2+2+2] Cycloadditon reaction between diynes and aldehydes/ketones 64 in the presence of [Ni(COD)J/SIPr...

Pyrans constitute another class of oxygen-containing heterocycles that have been prepared from Ni-catalyzed cycloaddition reactions. The coupling of diynes and aldehydes could be mediated by the combination of a Ni(0)... 

Bis( 1,5-cyclooctadiene) nickel (0 ) I tri-iQYi-butylphosphine 3,4>Fused pyran ring from diynes and aldehydes... 

Scheme 10.5 [(NHQNi]-catalyzed cycloaddition of diynes and aldehydes.

Diynes react with nitriles and aldehydes in the presence of a nickel(0) complex to give pyridines and dienones, respectively (Scheme 93).448,448a,448b... 

In sharp contrast to the unique pattern for the incorporation of carbon monoxide into the 1,6-diyne 63, aldehyde 77 was obtained as the sole product in the rhodium-catalyzed reaction of 1,6-enyne 76 with a molar equivalent of Me2PhSiH under CO (Scheme 6.15, mode 1) [22]. This result can be explained by the stepwise insertion of the acetylenic and vinylic moieties into the Rh-Si bond, the formyl group being generated by the reductive elimination to afford 77. The fact that a formyl group can be introduced to the ole-finic moiety of 76 under mild conditions should be stressed, since enoxysilanes are isolated in the rhodium-catalyzed silylformylation of simple alkenes under forcing conditions. The 1,6-enyne 76 is used as a typical model for Pauson-Khand reactions (Scheme 6.15, mode 2) [23], whereas formation of the corresponding product was completely suppressed in the presence of a hydrosilane. The selective formation of 79 in the absence of CO (Scheme 6.15, mode 3) supports the stepwise insertion of the acetylenic and olefmic moieties in the same molecules into the Rh-Si bond. 

However, the tricyclization of terminal diyne-al 224 at 60°C for 68 h gave fused 5-7-5 lactone 225 and aldehyde 226 (Scheme 100). The kinetic product was not isolated in this case. Thus, the preferential formations of222 and 225 indicate that the two endo-double system is substantially more favorable than the two exo-double bond system. 

The Rh(I)/dppf complex-catalysed 2-i-2-i-2-cycloaddition of oximes and diynes formed substituted pyridines in moderate to good yields (88%), under mild conditions. A one-pot procedure has been developed using aldehydes.The Ni-catalysed 2 -I-2 -I-2-cycloaddition of isocyanates (117) with 1,3-dienes (118) in MeCN produced 6-substituted dihydropyrimidine 2,4-diones (119). A key intermediate in this reaction is a five-membered azanickelacyclic species (Scheme 35). " The enantioselective cationic Rh(I)-catalysed 2-i-2-i-2-cycloaddition of diynes and isocyanates formed axially chiral pyridones with high ees (82%). The unique source of chirality is provided by a system containing [Rh(cod)Cl]2, l,4-bis(diphenylphosphino)butane, and the silver phosphate salt Ag(5)-TRIP. " " The Rh-catalysed 2-I-2-I-2-cycloaddition of diynes to sulfonimines in DCE, at r.t. to 80 °C, yielded 1,2-dihydropyridines in good yields (54-86%) and enantioselectivity (61-96%... 

As shown in Scheme 3, diyne monomers 5a-f were designed to react with a series of commercially available amines and aldehydes. The polymerizatiOTi of diyne 5a, L-phenylalanine methyl ester hydrochloride 6, and formaldehyde 7 was first investigated and the effects of solvent, temperature, time, concentration. 

Reductive Coupling of Conjugated Enynes and Diynes with Activated Aldehydes and Imines... 

Under these conditions, a variety of linear aliphatic terminal alkynes were transformed into aldehydes with good selectivity. The efficiency, regioselec-tivity of the addition and substituent tolerance were improved by using RuCl(Cp)(phosphine)2, where Cp is cyclopentadienyl, or RuCl(Cp)(diphos-phine) as catalyst precursors [30]. The best results were obtained with diphenylphosphinomethane as a ligand, which made possible the preparation of aldehydes from bulky aliphatic alkynes (tert-BuC=CH), aromatic alkynes (PhC=CH), diynes [HC=C(CH2)6C=CH] and functional terminal alkynes [NC(CH2)3C=CH, PhCH20(CH2)2C=CH,...]. The mechanism of this reaction was investigated in details by isolation of intermediates, deuterium-... 

Phase-transfer catalysis is a useful procedure for a variety of interesting metal-catalyzed reactions. - However, only one example of this approach has been reported for the synthesis of diynes by the sp-sp carbon coupling reaction. Thus vinylic dibromides derived from aromatic aldehydes have been shown to react with carbon monoxide, in the presence of zerovalent palladium compounds as the metal catalyst, and under phase-transfer conditions in a two-phase system (benzene, 5 M NaOH), to give the corresponding diynes in reasonable yields (equations 21 and 22). ... 

Corey reported a racemic synthesis of 11,12-LTA4 beginning with undeca-2,5-diyn-l-ol and forming the racemic epoxy aldehyde 28 (Scheme 4.11) The remainder of the synthesis parallels his approach to LTA4. 

Transition-metal-catalyzed hetero-[2 + 2 + 2]-cy-cloaddition of alkynes with carbon—heteroatom multiple bonds, such as isocyanides, carbon dioxide, nitriles, aldehydes, and ketones, provides heteroare-nes and unsaturated heterocycles. This reaction can be categorized into two groups one is the reaction of l,a>-diynes 397 with carbon—heteroatom multiple bonds, and the other is reaction of the alkynes 399, having a carbon—heteroatom multiple bond with alkynes as illustrated in Scheme 127. The reaction of 1,6 -diynes 397 proceeds through formation of the metalacyclopentadiene intermediate 398 followed by insertion of a carbon—heteroatom multiple bond, such as heterocumulenes (route a),189 nitriles (route b),190 and carbonyls (route c).191 On the other hand, the... 

Recently, Myers cyclizations were used to synthesize naphthalenic and benz[e]indene systems. Grissom and co-workers have constructed them from ene-diyne vinyl ether precursor 128 [46], The major pathway involves a Claisen rearrangement of 128 to provide the enyne-allene intermediate 129, which quickly undergoes Myers cycliza-tion to provide aldehyde 131 (Scheme 23). Bergman cyclization of the ene-diyne system to yield the tricyclic ether, 134, constitutes the minor pathway. 

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