Reactions of activated aryl sydnones with electrophiles

Electrophilic substitution on the aryl or sydnone ring of some ortho-substituted activated N-aryl-sydnones is reported.     

Stereochemistry in the reaction of alkylsulfinyl phenylmethyl carbanion with electrophiles

Stereochemistry of the reactions of methyl-, ethyl-, 2-propyl-, and 1,1-dimethylethylsulfinyl phenylmethyl carbanions with deuterium oxide and methyl iodide in tetrahydrofuran have been studied. The 2-propylsulfinyl phenylmethyl carbanion exerts abnormal behavior in the sense that the alkyl substituent herein has no ability to freeze the conformation of the carbanion. The results are interpreted in terms of hard and soft interactions. ⁷Li and ¹⁷O nuclear magnetic resonance (NMR) spectroscopy revealed that the carbanions derived from these sulfoxides behave as the oxylate form.     

Palladium-catalyzed cross-coupling reaction of alkynylzincs with benzylic electrophiles

The reaction of alkynylzinc bromides with benzyl bromides or chlorides in the presence of a catalytic amount of Pd(DPEphos)Cl₂ in THF at 23 °C cleanly produces the corresponding benzylated alkynes in 73-97% yields. With 10⁻³ mol % of Pd(DPEphos)Cl₂, the maximum turnover number of 7.1 × 10⁴ has been observed for the formation of PhCCCH₂Ph.     

Novel palladium complex-catalyzed reaction of magnesium amides with allylic electrophiles

Conclusions A novel method has been described for the efficient formation of nitrogen-carbon bonds via the reaction of magnesium amides with functionalized nitrogen, oxygen, and sulfur-containing allylic derivatives, catalyzed by transition metal complexes. New high (molecular weight) unsaturated tertiary amines have been prepared.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 406–409, February, 1987.     

An activated building block for the introduction of the histidine side chain in aliphatic oligourea foldamers

A new N-Boc-protected monomer for the synthesis of oligourea foldamers containing the (1H-imidazolyl-4yl)methyl side chain of histidine, has been prepared in seven steps from Trt-His(τ-Trt)-OMe. This protecting group combination on histidine was found to be critical to ensure efficient access to the requisite activated building block. This new derivative, suitable for solid phase synthesis, expands the current arsenal of building blocks with proteinogenic side chains useful for the design of peptidomimetic oligourea foldamers.     

The molecular weight distribution for chain polymerization plus side reaction

The kinetics of chain polymerization is investigated for the case of a complicating side reaction. In addition to the polymerization reaction, A_i + M → A_i+1, there is a reversible side reaction, A_i + Q ↔ B_i. Initiation is assumed to be instantaneous. The monomer concentration M, and the concentration of the reacting species Q, are assumed to be constant. The reaction kinetics are solved exactly, yielding the distribution of living and dormant polymer, as well as the molecular weight distribution, as explicit functions of the reaction rate constants and the time. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1711–1725, 1997     

One-pot Pd-catalyzed hydrostannation/Stille reaction with acid chlorides as the electrophiles

A one-pot hydrostannation/Stille coupling sequence amenable to the employment of acid chloride electrophiles has been developed. In this protocol, palladium mediated alkyne hydrostannations using Me₃SnF/PMHS as an in situ trimethyltin hydride source are followed by the addition of the acid chloride to afford a variety of α,β-unsaturated ketones in a single pot.     

Generation of sec-thioamide dianions and their regioselective reaction with electrophiles.

The enolates of sec-thioamides $\text{8}$, which are generated by three different methods (scheme II and equation 1), are alkylated selectively at the α-carbon to the thiocarbonyl group. The unusual β′-lithiation to provide an intermediate $\text{11}$ is observed for N-methyl-α, β-dimetylthioacrylamide and N-methyl-thiocyclohexenecarboxamide.     

Atom-efficient metal-catalyzed cross-coupling reaction of indium organometallics with organic electrophiles.

The novel metal-catalyzed cross-coupling reaction of indium organometallics with organic electrophiles is described. Triorganoindium compounds (R(3)In) containing alkyl, vinyl, aryl, and alkynyl groups are efficiently prepared from the corresponding lithium or magnesium organometallics by reaction with indium trichloride. The cross-coupling reaction of R(3)In with aryl halides and pseudohalides (iodide 2, bromide 5, and triflate 4), vinyl triflates, benzyl bromides, and acid chlorides proceeds under palladium catalysis in excellent yields and with high chemoselectivity. Indium organometallics also react with aryl chlorides as under nickel catalysis. In the cross-coupling reaction the triorganoindium compounds transfer, in a clear example of atom economy, all three of the organic groups attached to the metal, as shown by the necessity of using only 34 mol % of indium. The feasibility of using R(3)In in reactions with different electrophiles, along with the high yields and chemoselectivities obtained, reveals indium organometallics to be useful alternatives to other organometallics in cross-coupling reactions.     

The metathesis reaction for side chain construction in carbocyclic sinefungin analogue synthesis

The naturally occurring nucleoside sinefungin has found considerable use in biological investigations. More extensive sinefungin studies have been limited because few analogues have been reported due to the synthetic challenges associated with such studies. Reported herein are preparative ways to two carbocyclic sinefungin analogues: 6′-deaminocarbocyclic sinefungin and (S)-6′-hydroxy-6′-deaminocarbocyclic sinefungin. The synthetic routes were made efficient and practical by the application of two metathesis reactions employing second generation Grubbs catalyst.     

One-pot asymmetric conjugate addition-trapping of zinc enolates by activated electrophiles

The copper-catalyzed asymmetric conjugate addition of dialkyl zinc leads to homochiral zinc enolates. These intermediates were trapped in situ with activated allylic electrophiles, without the need of additional palladium catalysis. High trans selectivity (85/15 to 100/0) and excellent enantioselectivities (up to 99%) could be attained. The functionalized nature of the electrophiles makes the new synthons potential candidates for further elaboration.     

The reaction of 4-(p-nitrobenzyl)pyridine with some electrophiles

The nucleophile 4-(p-nitrobenzyl)pyridine was allowed to react with four carcinogenic alkylating agents, chloromethyl methyl ether, bis(chloromethyl) ether, glycol sulfate and propane sultone, one carcinogenic acylating agent, N,N-dimethylcarbamyl chloride, and one noncarcinogenic electrophile, perchlorocyclobutenone. The structures of the major products formed, which are substituted pyridinium salts or 1,4-dihydropyridines, were determined.     

Regioselective deprotonation of 3-methyl-4,5-dihydroisoxazoles and diastereoselective reaction with electrophiles

Highly regioselective deprotonation of the title compounds is achieved by working with lithium-amide bases of different steric requirement. The effect of a 5-alkoxymethyl group in theΔ²-isoxazoline ring on both the sense and the extent of the stereoselectivity observed in the reaction of C₄-anion with electrophiles is discussed.     

Unexpected regiochemistry in the reaction of some γ-trimethylsilylated 3-dialkylamino-crotonate esters with carbonyl electrophiles.

4-Trimethysilyl-3-dialkylaminocrotonate esters ($\text{4}$) react with a number of carbonyl electrophiles and titanium tetrachloride to give products with substitution at γ-position. A dynamic equilibrium of $\text{4}$ and its O-silyl isomer $\text{16}$ is proposed to explain the regiochemistry.     

Controllable highly stereoselective reaction of in situ generated magnesium dienolate intermediates with different electrophiles

In this paper, we have described an efficient controllable stereoselective alpha-acylation and -allylation reaction of the magnesium dienolate intermediates generated in situ from the Fe(III)-catalyzed reaction between 2,3-allenoates and Grignard reagents with different electrophiles to afford 2-acylated or allylated 3( Z)- or ( E)-alkenoates depending on the nature of the electrophiles and reaction conditions. The distinct stereoselectivity may be caused by the isomerization of metallic Z-1,3-dienoate to E-1,3-dienoate via the intermediacy of anti-allylic MgCl and syn-metallic species.     

β-Nitrostyrenes as electrophiles in Parham cyclization chemistry: reaction with o-lithiobenzonitrile

β-Nitrostyrenes react with o-lithiobenzonitrile, generated from the requisite aryl bromide at −100 °C by bromine-lithium exchange with n-butyllithium in THF, to afford 2-nitro-3-phenyl-3H-inden-1-ylamines resulting from 1,4-addition to the β-nitrostyrene followed by intramolecular capture of the resultant nitronate anion by the ortho-cyano functional group.     

Addition reaction of spiro orthoesters with electrophiles: A model reaction for the development of novel polyaddition accompanying ring-opening isomerization

The addition reaction of spiro orthoesters (SOEs) with electrophiles accompanying ring-opening isomerization was investigated as a model reaction for polyaddition of bifunctional SOEs with bifunctional electrophiles. Among several electrophiles such as carboxylic acids and carboxylic anhydrides, acid halides showed particularly high reactivities to SOEs. An equimolar reaction of SOEs with acid chlorides took place selectively, leading to the corresponding 1 : 1 adducts. SOEs with seven-membered cyclic ether rings—1,4,6-trioxaspiro[5.6]undecane derivatives—showed higher reactivities than SOEs with six- and five-membered cyclic ether rings. The reaction accompanied zero shrinkage in volume. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4502–4509, 1999     

Synthesis of macrocyclic lactones with methoxysulfonyl side chain

Two representative macrocyclic lactones with methoxysulfonyl side chain（5a and 5b）were synthesized employing Michael addition with acrolein and ring enlargement as the key steps,starting from potassium,α-oxocycloaikylsulfonates（1）in total yields of 45 and 57%,respectively.