Ethyl substituent

As numbered on the structural formula the longest continuous chain contains eight car bons and so the compound is named as a derivative of octane Numbering begins at the end nearest the branch and so the ethyl substituent is located at C 4 and the name of the alkane is 4 ethyloctane... 

The key here is to recognize that an ethyl substituent can be introduced by Fnedel-Crafts acylation followed by a Clemmensen or Wolff-Kishner reduction step later in the syn thesis If the chlorine is introduced prior to reduction it will be directed meta to the acetyl group giving the correct substitution pattern... 

Polymer Modification. The introduction of functional groups on polysdanes using the alkah metal coupling of dichlorosilanes is extremely difficult to achieve. Some polymers and copolymers with 2-(3-cyclohexenyl)ethyl substituents on siUcon have been made, and these undergo hydrogen hahde addition to the carbon—carbon double bond (94,98). 

This procedure is representative of a new general method for the preparation of noncyclic acyloins by thiazol ium-catalyzed dimerization of aldehydes in the presence of weak bases (Table I). The advantages of this method over the classical reductive coupling of esters or the modern variation in which the intermediate enediolate is trapped by silylation, are the simplicity of the procedure, the inexpensive materials used, and the purity of the products obtained. For volatile aldehydes such as acetaldehyde and propionaldehyde the reaction Is conducted without solvent in a small, heated autoclave. With the exception of furoin the preparation of benzoins from aromatic aldehydes is best carried out with a different thiazolium catalyst bearing an N-methyl or N-ethyl substituent, instead of the N-benzyl group. Benzoins have usually been prepared by cyanide-catalyzed condensation of aromatic and heterocyclic aldehydes.Unsymnetrical acyloins may be obtained by thiazol1um-catalyzed cross-condensation of two different aldehydes. -1 The thiazolium ion-catalyzed cyclization of 1,5-dialdehydes to cyclic acyloins has been reported. 

The hydroxyl group is lost from a carbon that bears three equivalent ethyl substituents. Beta elimination can occur in any one of three equivalent directions to l give the same alkene, 3-ethyl-2-pentene. ... 

The steric crowding introduced in the latter by the four ethyl substituents inhibits nucleophilic attack at platinum, so that complexes of this type tend to undergo substitution by a dissociative mechanism [89]. The complex of the more rigid ligand, 2,2, 2"-terpyridyl, Pt(terpy)Cl+, is found to be about 103 to 104 times more reactive to substitution than the dien analogue this is ascribed to steric strain [90], which is reflected in the short Pt—N bond to the central nitrogen (Pt-N some 0.03 A shorter than the other two Pt-N bonds) and N—Pt—N bond angles of 80-82°). 

Recognize molecular symmetry planes and axes. Even approximate, or local symmetry elements may be useful. One should not step back just because, formally, the molecule has no symmetry elements. A methyl and an ethyl substituent, or chlorine and bromine substituent, can be equated. Substituents that disrupt the molecular symmetry but have trivial electronic requirements may be deleted. 

The main mass fragmentation of secobenzylisoquinoline alkaloids involves bond cleavage between the two benzylic carbonyls. This process is evidenced by the presence of peaks representing fragment ions at m/z 151, found in spectra of all these bases and attributed to the lower portion of the molecules, and ions at m/z 220,236, and 222, found in spectra of 159,160, and 161, respectively, formed from the upper part of the compounds. Similarly, as in the mass spectra of other secoisoquinoline alkaloids incorporating the amino-ethyl substituent, the [H2C=N(CH3)2]+ ion at mjz 58 is the base peak. 

Cyclopropane ring openings have been proposed to account for the biosynthesis of several unconventional sterols. Ficisterol (106) [70, 71] is of the 26-norergostane type and contains the rare 23-ethyl substituent. Its biosynthesis became apparent following the isolation of the trace cyclopropane sterol,... 

High oxidation state alkylidene complexes in which a heteroatom is bound to the alkylidene carbon atom are extremely rare [41]. Since the approach shown in Eq. 43 failed, the related approach shown in Eq. 44 was taken to prepare the medium-sized ring subunits [222]. The latter product was formed in good yield when n=2, R H, R2=Et, but only poor yield when n=2, R =Et, R2=H, possibly due to unfavorable interactions between the ethyl substituent and transannular groups in the transition state for cyclization of the allyl ether [222]. Ruthenium catalysts either failed or gave low yields, presumably because of the steric hindrance associated with ring-closing dienes of this type. 

In their study of the conformations of oligosilanes with methyl and ethyl substituents,9 Michl and co-workers pinpointed the specific substituent-substituent interactions in tetrasilanes responsible for inducing C, Z), and A conformations, allowing a prediction of backbone dihedral angle and direction of twist, given a specific arrangement of ethyl groups. 

Despite this superficial similarity, however, subtle differences between the behaviour of ionized amines and the analogous ionized alcohols and ethers remain. Thus, metastable ionized 2-butylamine loses 80% ethane in contrast, ionized 2-butanol eliminates both ethane (35%) and methane (40%)85. The latter reaction corresponds to loss of the smaller methyl group and an a-hydrogen atom from the larger ethyl substituent at the branch point. Methane loss does not occur from ionized amines with a methyl substituent on the -carbon, with the solitary exception of ionized isopropylamine which does expel methane (10%). However, ionized 3-hexylamine eliminates both ethane (35%) and propane (20%)85. 

Probably, with ethyl substituent, a 7t-allylic adsorption [such as suggested by Paal and Dobrovolszky (97)] competes with the dual site mechanism. 

The lack of any directing effect from the 4-methoxy and the 5-ethyl substituents at the two stereocenters already present in 71 is a remarkable finding, and points to strong catalyst-dependence in the stereocontrol (Scheme 7.20). On the basis of these findings, various stereoisomers of 3,4,4,5-tetrasubstituted cyclohexanones are now accessible through sequential catalytic 1,4-additions, with control over the relative and absolute configurations possible simply by judicious selection of the appropriate enantiomer of the chiral ligand in each step. 

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