Secondary acyclic

Imide-terminated telechelics are also synthesized by metathesis depolymerization, and it is found that phthalimide-substituted olefins allow for productive depolymerization when only one methylene spacer separates the nitrogen atom and the olefin (Fig. 8.21). This combination of steric hindrance around the nitrogen lone pair and decreased electron donation from resonance prevents the negative neighboring group effect. However, secondary acyclic amines are unable to produce telechelics through metathesis depolymerization because of unfavorable catalyst-amine interactions. 

The salient points in this diagram are (i) the rate-determining step in the interconversion 55 6 is the bond-making (or bond-breaking) between the secondary C+ and CO (ii) the rate of carbonylation of the secondary pentyl ion 10 (and presumably also of other secondary acyclic alkyl cations) in FHSO3—SbFs has a free-enthalpy of activation of about... 

The known examples of carbenoid insertion into an S—H bond have been supplemented by the Rh2(OAc)4-catalyzed synthesis of a-phenylthioketones from a-diazoketones and thiophenol 327). By this method, a number of primary and secondary acyclic a-diazoketones, ethyl diazoacetate and cyclic diazoketones such as 2-diazocyclopentanone, 2-diazo-6-methylcyclohexanone and 2-diazocyclohepta-none were converted at room temperature in good to high yield. 

The A-Boc group also activates secondary acyclic amines toward deprotonation, and unsymmetrical amines may be deprotonated regioselectively in some instances. For example, selective deprotonation of a methyl proton over a methylene can be expected, as shown by the example in Scheme 30a. Similarly, regioselective removal of a cyclopropyl proton occurs in preference to a methylene, as shown in Scheme 30b. 

The alkenyl hydroperoxides and polymeric dialkyl peroxides are fairly stable at ambient temperature but decompose appreciably at the reaction temperatures studied. Thermal stabilities of the alkenyl hydroperoxides and dialkyl peroxides in the olefin solution were determined by heating the solution at 110°C. under nitrogen. The peroxide numbers were plotted vs. time to estimate the half-lives in solution. The thermal decomposition half-lives of these alkenyl hydroperoxides are compared with values from the literature for acyclic and cyclic hydroperoxides in Table IV. Secondary acyclic alkenyl hydroperoxides appear to be less... 

For secondary acyclic allylic alcohol benzoates, resolved by Sharpless enantioselective epoxida-tion, there is a similar relation between the sign of the benzoate Cotton effect and absolute configuration, as in 7 and 8149. 

Secondary acyclic amides in the solid state display an amide II band in the region of 1570-1515 cm-1. In dilute solution, the band occurs in the 1550-1510 cm-1 region. This band results from interaction between the N—H bending and the C—N stretching of the C—N—H group. A second, weaker band near 1250 cm-1 also results from interaction between the N—H bending and C—N stretching. 

Secondary acyclic formamides RNHCH=0 can serve as efficient /V-nuclcophiles in the addition to nitroalkenes R1CH=C(R2)N02 to afford the corresponding Michael adducts in good yields.188... 

On the other side of the scale, very moderate, but not negligible, Lewis acidities are ascribed, according to their a parameters, to C-H acids, such as chloroform and bromoform, primary and secondary acyclic amines, such as -butylamine and diethylamine, and protogenic solvents, such as methyl-alkyl ketones, acetonitrile, and nitromethane. It can be expected that liquid 1 -alkynes (not on the List), having the grouping H-C=C-R, also have non-negligible a values, being C-H Lewis acids. It can be safely concluded, however, that aprotic solvents other than those of the classes noted above have no Lewis acid character, with a 0 for all intents and purposes. 

Reaction of Secondary Acyclic Amines with Aryl Sulfonates. 159... 

Whiting has reported product analyses on the rearrangement of cis-and acetic acid (White and Stuber, 1963) may also be mentioned. 

BzCl or BZ2O, Pyr, 0 C. Benzoyl chloride is the most common reagent for the introduction of the benzoate group. Reaction conditions vary, depending on the nature of the alcohol to be protected. Cosolvents such as CH2CI2 are often used with pyridine. Benzoylation in a polyhydroxylated system is much more selective than acetylation. A primary alcohol is selectively protected over a secondary allylic alcohol, and an equatorial alcohol can be selectively protected in preference to an axial alcohol," but this has been shown to be solvent dependant in some cases." A cyclic secondary alcohol was selectively protected in the presence of a secondary acyclic alcohol. ... 

Doyle s catalysts and methodology have been extended to C-H insertion reactions of diazoacetates derived from secondary acyclic and cyclic alcohols where diastereoselectivity becomes an integral component of the overall stereocontrol objective. Two outstanding examples in the acyclic series are shown in Scheme 11... 

J. G. Verkade has synthesized a series of bicyclic triamino phosphines that are potent a-donors to palladium, yet can be modified to incorporate a variety of steric encumberance.46 It was found that ligand L13 could promote the catalytic amination of both aryl chlorides and bromides with secondary cyclic amines and anilines. L13 was not as effective for aliphatic secondary acyclic amines and primary aliphatic amines. The scope was improved with ligand L14, but as with other third generation ligands, primary aliphatic amines were prone to giving de-halogenated arene. 

Verkade was able to aminate aryl bromides and chlorides where R1 contains an acidic proton (phenol, amide, or ketone) by simply using 2.4 equiv of LiHMDS rather than the usual 1.4 equiv. NaO/-Bu.46a This procedure works well for cyclic secondary amines and anilines of all types, but gives poor yields for primary aliphatic and secondary acyclic amines. 

The Buchwald series of bulky phosphines containing the tunable bi-aryl moiety have also been shown to allow for the efficient animation of aryl chlorides as well.57 In particular, Pd/L3 catalyzed the reaction between secondary cyclic amines and most aryl chlorides at 80 °C, Secondary acyclic amines and anilines tend to couple best with neutral to electron rich aryl chlorides. Primary aliphatic amines are quite limited to either the amination of o-tolyl chlorides, or more activated primary amines such as benzyl amine. A better ligand for this transformation was reported to be L4 as the amination could be conducted at room temperature in many cases.58 Base sensitive R1 required the use of K3PO4 rather than NaOf-Bu. Most amines work well with this catalyst system, except for unactivated primary aliphatic amines (e.g., n-hexyl amine). Allyl amine, hydrazines, imines, benzyl amine, and (EtO)2CH2NH2 all couple well with aryl chlorides under the... 

M. Beller reports an improved phosphine ligand for aryl chloride amination based on //-phenyl indoles, L16 or L17. This class of ligands allows for the catalytic amination of aryl chlorides with primary aliphatic amines and anilines. Secondary cyclic amines also couple, but secondary acyclic amines were not reported. 

Hartwig initially demonstrated that SIPr carbene ligand with Pd(dba)2 is an excellent catalyst for the amination of ArCl with secondary cyclic amines, secondary acyclic amines, and anilines.62 Primary amines were low yielding, except with benzyl amine. Nolan s catalyst, (SIPr)Pd(cin)Cl, gave room temperature amination of aryl chlorides in DME with all secondary amines and anilines. Primary aliphatic amines were reported to work well starting with Pd2(dba)3 and IPr-HCl using KOr-Bu in dioxane. Typically, electron neutral and electron rich aryl chlorides are the best substrates. 

Primary tosylates are more prone than bromides to form f-butyl ethers by Sn2 displacement by the f-butoxide anion in DMSO. Sulfonate esters of flexible cyclic and secondary acyclic alcohols give predominately alkenes in the presence of f-BuOK/DMSO. With sulfonate esters of 3-hydroxy steroids, there is competition between /S-elimination and attack of the f-butoxide ion on sulfur to form alcohols mesylates are more prone to this reaction than tosylates. Sulfonate esters of 3a-acetoxy-12a-hydroxycholanate undergo mainly /3-elimination with f-BuOK/DMSO (eq 4). In this case, substitution of various other aprotic solvents for DMSO and DMSO Na+ for f-BuOK was not as effective. Treatment of both the mesylate and the tosylate of cholesterol with f-BuOK/ DMSO gives the conjugated diene, 3,5-cholestadiene, in high yield. ... 

Two separate reports on the vanadium-catalysed epoxidation of allylic alcohols have appeared. In the case of secondary acyclic E -allylic alcohols opposite stereospecificity to peracid and molybdenum-catalysed systems is observed. This... 

Removal of the ester group afforded the cephalosporin acid (205). 7-Amino- and 7-acylaminocephalosporin esters directly substituted at position 3 with a secondary acyclic amino group or a cyclic secondary amino group were reduced in dry solvents with diborane to yield 3-unsubstituted 3-cephems. The same 3-aminocephalosporins were reacted with an alkyl or aryl Grignard reagent to afford the corresponding 3-alkyl- or 3-aryl-3-cephem esters (U.S. Patent 4,065,618). 

MeO secondary acyclic, primary aryl, primary alkyl... 

---