1,4-nudeophilic addition

The addition of methanol or hydrazoic acid to ethenylidenecydopentadiene 3 demonstrates that 3 behaves like an acceptor-substituted allene (Scheme 7.27) [226, 227]. More examples of nudeophilic additions to alkyl-substituted derivatives of 3 were reported by Hafner [228]. Photoelectron spectroscopy of the spirocyclic compound 165b, easily accessible from azide 164b, shows that the lone-pair orbital n(N) of the 2H-azirine nitrogen atom interacts strongly with the Jt1-orbital of the cyclo-pentadiene ring [227]. 

Intermediates such as 224 resulting from the nudeophilic addition of C,H-acidic compounds to allenyl ketones such as 222 do not only yield simple addition products such as 225 by proton transfer (Scheme 7.34) [259]. If the C,H-acidic compound contains at least one carbonyl group, a ring dosure is also possible to give pyran derivatives such as 226. The reaction of a similar allenyl ketone with dimethyl mal-onate, methyl acetoacetate or methyl cyanoacetate leads to a-pyrones by an analogous route however, the yields are low (20-32%) [260], The formation of oxaphos-pholenes 229 from ketones 227 and trivalent phosphorus compounds 228 can similarly be explained by nucleophilic attack at the central carbon atom of the allene followed by a second attack of the oxygen atom of the ketone at the phosphorus atom [261, 262], Treatment of the allenic ester 230 with copper(I) chloride and tributyltin hydride in N-methylpyrrolidone (NMP) affords the cephalosporin derivative 232 [263], The authors postulated a Michael addition of copper(I) hydride to the electron-... 

The intermediate product 162, formed from the nudeophilic addition of 1,2-alle-nic phosphonate or 1,2-allenic phosphine oxide with allylic alcohol, would also undergo a Claisen rearrangement to form 2-oxo-5-alkenyl phosphonate or phosphine oxide 163 [85], The rearrangement is accelerated by the carbanionic nature of the intermediate 162. For the conjugate addition step, the reaction temperature is crucial since the reaction at 0 °C afforded mainly /i,y-unsaturated product whereas a,/8-unsaturated products were formed at 20 °C. 

Osman, R., Namboodiri, K., Weinstein, H. and Rabinowitz, J.R. (1988) Reactivities of acrylic and methacrylic adds in a nudeophilic addition model of their biological activity. J. Am. Chem. Soc., 110, 1701-1707. 

Matsumoto, M. Watanabe, N. Ishikawa, A. Murakami, H. Base-induced cydization of 1-benzyloxy-2,2,4,4-tetramethylpentan-3-ones intramolecular nudeophilic addition of an anion of a benzyl ether to the carbonyl moiety without Wittig rearrangement or protophilic decomposition. Chem. Commun. 1997, 2395— 2396. 

The transformation of2-734 involves an initial generation of an organosamarium species 2-735 with subsequent nudeophilic addition to the lactone carbonyl. Presumably, a tetrahedral intermediate 2-736 is formed that collapses to yield the ketone 2-737. This reacts with Sml2 to give a ketyl radical 2-738, which undergoes an intramolecular 5-exo radical cydization reaction with the alkene moiety. The resultant... 

Coi jugate Nudeophilic Addition to Opp-Unsaturated Aldehydes and Ketones 786... 

Nudeophilic (Addition of llie pcpU-d t rmiti ) aniitio group to phenyl inothiocyanateiPtTC) yields on N-phenylthiDuiva derivotm. 

Silylcuprates have been reported to undergo reactions with a number of miscellaneous Michael acceptors [65]. Conjugate addition to 3-carhomethoxy acyl pyri-dinium salts [65a] affords 4-silyl-lj4-dihydropyridines. Oxidation with p-chloranil generates a 4-acyl pyridinium salt that gives the 4-silylnicotinate upon quenching with wateq and methyl 4-silyl-2-suhstituted dihydronicotinates upon quenching with nudeophiles (nudeophilic addition at the 6-position). The stabilized anion formed by conjugate addition to an a, -unsaturated sulfone could he trapped intramolecularly by an alkyl chloride [65h]. 

The Nudeophilic Addition/Ring Closure (N ARC) Sequence for the Stereocontrolled... 

Krohn K (1990) Synthesis of anthracydinones by electrophilic and nudeophilic addition to anthraquinones. Tetrahedron 46 291... 

Step 2 Structure II still has no leaving group that can depart (Break a bond) given the acid media. We cannot protonate a second time (Add a proton) because doing so would create a dication, and if we take off the proton (Take a proton away), that simply leads back to I. So by process of elimination, we predict that there must be nudeophilic addition to give ni. Therefore, Make a bond between a nucleophile and an electrophile. 

Note here what makes the chemistry of aldehydes and ketones different from that of acids (or esters). In the aldehydes and ketones there is no leaving group present, whereas in an add (or ester) there is (Fig. 17.25). The chemistry of aldehydes and ketones on the one hand, and the chemistry of acids and esters on the other, diverge only after the nudeophilic addition of the alcohol to the carbonyl (see Fig. 17.21). In the acids and esters there is a group that can be lost, providing a route to other molecules in the aldehydes and ketones there isn t, which means that the adds and esters can imdergo an addition-elimination reaction that the aldehydes and ketones can t. 

Nudeophilic Addition Reactions tfAryl and ASkenfIbofonic Acids and Their Derivatives to Imines... 

Nudeophilic Addition Reactions of Aryl and Alkenylboronic Acids and Their Derifatiires to Imines... 

Nudeophilic addition reactions of aryl and alkciiylboronic acids to imine deiivativcs (Batcy)... 

For the acid-catalyzed process, the transition state of a (2 + 2 + 2)-cydoaddition is postulated, whereas the base-catalyzed reaction is thought to proceed by a series of nudeophilic additions. Arylcyanides, arylcyanates, and cyano compounds with electron-attracting substituents (e.g., COOR, Cl) are most suitable for the cydotrimerization. Alkylcyanides trimerize only at high temperature and pressure in moderate yidds. 

Classes of Nudeophile Addition Pathways to Multihapto-Complexes... 

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