Preparation by Nucleophilic Addition

Preparation by Nucleophilic Addition.- The monoanion of 1, 4-dioxene has been developed as a two-carbon homologating agent for converting carbonyl compounds into B-keto-alcohols via an addition- 

Cerium(III) chloride has been reported to promote nucleophilic addition of Grignard reagents to ketones, generating tertiary 

Metallic zinc has also been used to allylate carbonyl compounds 

The presence or absence of HMPA in the reaction medium has been 

Nickel, produced in situ by reduction of nickel(II) iodide with lithium-naphthalene (Vol.8, p.233), can be used to carry out 

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A urethane is typically prepared by nucleophilic addition reaction between an alcohol and an isocyanate (R—N = C=0), so a polyurethane is prepared by reaction between a cliol and a diisocyanate. The diol is usually a low-molecular-weight polymer (MW 1000 amu) with hydroxyl end-groups the diisocyanate is often toluene-2,4-diisocyanate. 

In the intense search for inhibitors of gastric acid secretion a new class of potent histamine H2-receptor antagonist was discovered. These 1,2,5-thiadiazole-l-oxides (27) were prepared by nucleophilic addition of primary amines to 3,4-dialkoxy-l,2,5-thiadiazole 1-oxide (25). Sequential addition of two different amines to positions C(3) and C(4), respectively, could be achieved via the 3-alkoxy-4-amino adduct (26) (Scheme 5) <82JMC207,82JMC210>. 

Thermolysis of 3-(ort o-anisoyl)-l-(l-piperidinyl)-3-cyclobutenes 807 in the presence of mesitylene affords angular-fused xanthones 809 via formation and ring closure of the intermediate 808 (Scheme 226) <1997TL3663>. Linear-fused xanthones 810 are prepared by nucleophilic addition of aryl and heteroaryl lithiates to dithiane protected benzopyrone-fused cyclobutenediones 811 followed by hydroysis of the dithiane protecting group (Scheme 227) <1996JA12473>. 

The bicyclic isoxazolidine 76 was prepared by nucleophilic addition of 2-trimethylsilyloxyfuran to A-gulosyl-nitrones and employed in a formal synthesis of Polyoxin... 

The other product is 6 -methoxyquinoline 11a that is obtained in high purity as almost colorless crystals, with only a slight yellow tinge. Previously, this heteroaromatic material was available commercially only as a brown mass. Derivatives with substituents at C2 and C4 have been prepared by nucleophilic addition to the pyridine nucleus (Figure 12.1). 

In addition to the previous methods for generating ( )-a,p-unsaturated aldehydes, a one-pot preparation of a,P-unsaturated-a-substituted aldehydes has been reported (Scheme 5.84).3 The procedure involves the intermediacy of lithiated a,p-enaminophosphonates, which are prepared by nucleophilic addition of diethyl 1-lithioalkylphosphonates to ethyl A-phenylformimidate. The lithiated rz.p-cnarninophosphonate is reacted with aliphatic or aromatic aldehydes to produce a,P-unsaturated-a-substituted imines, which can be efficiently converted to a,p-unsaturated-a-substi-tuted aldehydes by acid hydrolysis in yields ranging from 45% to 78%. ... 

A new preparative method for allenes has appeared (Scheme 4). Several alk-2-ynyl carbonates (prepared by nucleophilic addition of magnesium and lithium acetylides to ketones or aldehydes followed by quenching with methyl chloroformate) were selectively hydrogenolysed with ammomium formate under palladium catalysis to give allenes in good yields. 

Alkyl p-tolyl sulfones have been prepared by nucleophilic addition of the p-tolyl sul-finate anion to primary, allylic, and benzylic halides in tetrahydrofuran [23]. Although these reactions were conducted in the presence of a stoichiometric amount of quaternary ammonium salt, it seems clear that the reaction could be catalytic and is therefore included here. The reaction is formulated in equation 13.13 and several examples of the condensation are shown in Table 13.9. 

The nucleophilic addition reaction is the most common general reaction type for aldehydes and ketones. Many different kinds of products can be prepared by nucleophilic additions. Aldehydes and ketones are reduced by NaBH4 or UAIH4 to yield primary and secondary alcohols, respectively. Addition of Grignard reagents to aldehydes and ketones also gives alcohols (secondary and tertiary, respectively), and addition of HCN delds cyanohydrins. Primary amines add to carbonyl compounds yielding imines, or Schiff bases, and secondary... 

Vinyl azides were seldom prepared by nucleophilic addition at alkynes lacking in strongly electron-withdrawing groups. Thus, the reaction of butadiyne (24) with lithium azide in methanol is such a rare case, which allows the isolation of enyne 25 as a yellow liquid. ... 

Aziridines can be prepared by nucleophilic addition to isolable 2/f-azirines. This is an important method for the synthesis of aziridines bearing a heteroatom substituent on position 2 or 3. Here we limit the examples to reactions in which vinyl azides are the starting materials and the intermediate 2H-azirines derived from them are not isolated, usually because they are unstable. 

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