Showing papers by "George M. Whitesides published in 1974"

Reactions of alkylmercuric halides with sodium borohydride in the presence of molecular oxygen

Abstract: Reaction of alkylmercuric halides with sodium borohydride in dimethylformamide saturated with molecular oxygen produces alcohols and borate esters in good yields. The products obtained following reaction of neophylmercuric bromide (l), 1,7,7-trimethylbicyclol2.2.llheptyl-2-mercuric bromide (9), and endoand exo-norbornyl-2-mercuric bromides (13 and l4) with borohydride in the presence of oxygen are compatible with a reaction mechanism involving free, noncaged, alkyl radicals as intermediates. This mechanism finds further support in the observations that rcaction of I with borohydride and oxygen in solutions containing2,2,6,6-tetramethylpiperidoxyl radical leads to good yields of thc prodr-rct of coupling of neophyl radical with the nitroxyl. Reaction of a-alkoxyl alkylmercuric halides with borohydridc and oxygen generatcs a-alkoxyl alcohols in good yields; similar reaction of a-hydroxy alkylmercuric halides does not lead to vicinal diols. [ lky l radicals are establ ished intermediates in the re11 duct ive c lemercurat ion of a lkylmercur ic hal ides by metal hydr ides.2-a The loss of stereochemistry that occurs during conversion of the carbon-mercury bonds of diastereomeric 2-norbornylmercury compounds into carbon-hydrogen bonds, the characteristic structural rearrangements that accompany demcrcurat ion of nortr icyclyhnercury compounds, and the absence of l , 2-phcnyl migration on reduction of neophylmercuric bromide combine to def ine the l i fet imes of the interrnediate alkyl radicals in these react ions to be short , br\"rt do not diffcrcntiate between radical-cage mechanisms (of which onc possible sequence is reprcscnted by eq 2 and 3) and rapid radical-chain reactions (eq 4 and 5) . ] I } I RHgBr --> RHgH RHgH --> R. + .HgH (2) R' + 'HgH ---> RH * Hg(O) (3)

Copper(I) alkoxides. Synthesis, reactions, and thermal decompositions

Abstract: Alkoxides and phenoxides of copper(I) can be prepared by the heterogencous reaction between alcohols and phenols and methylcopper(I). These organocopper(I) compounds are useful reagents for the formation of ethers by displacement of hai ide from organic hal ides. The reaction of copper(l) alkoxidcs with aryl hal ides yields alkyl aryl ethers under part icularly mild iondit ions. Thermal decomposit ion of primary alkorycopper(l) reagcnts generates intermediate alkoxy radicals. Thermal clecomposit ion of secondary alkoxycopper(l) reagents apparently can take place either by a free-radical mechanism or by a mechanism tentat ively suggested to involve copper(I)-hydride as an intermediate. The structural factors determining which mechanism wil l predominate for a given compound have not been established' tTth. utit i ty of alkyland arylcopper(l) reagents in I organic synthesis is based on their h igh nucleophi l ic i ty toward carbon, and on their abi l i ty to take part in electron-transfer reactions.2-a They also show low basicity toward protons, an afff inity for carboncarbon double bonds, and an abi l i ty to coordinate wi th soft Lewis bases. Since the mechanisms by which copper(I) influences the reactivity of carbanions are not clearly understood, it is diff icult to predict the behavior of new types of organocopper( I ) compounds. Nevertheless, there is obvious reason to hope that organic derivatives of copper(I) other than those belonging to the wel l -explored class of compounds containing carbon-copper bonds might also show useful (1) Supported by the Nat ional Science Foundat ior l , Grants GP28586X ancl GP-14247, ancl by the Internat ional coppcr Rcsearch Associat ion. (2) J. F. Normant, S) 'nthesis,2,63 (1972); G' H. Posner, Org' React ' , 19, | (1972), (3) G. Br ihr ancl P. Burba in \"Methoden der organischen chemie\" (Houben-Weyl) , Vol . XI I I /1, E ' Mi , i l ler , Ed. , Georg Thicme Vcr lag, Stut tgart , 1970, p 731 f f . (4) O. A. Chal tyk ian, \"Copper-Catalyt ic React ions,\" A. E. Stubbs, t rans. , Consul tants Bureau, New York, N' Y. , 1966; P. F. Fanta, Chem. Rec, ,64,613 (1964); R. G. R. Bacon and H. A. O. Hi l l ' Quart ' Rec. , Chem. Soc. , 19,95 (1965); J. Peisach, P. Aisen, and W. E' Blurnberg, Ed., \"The Biochemistry of Copper,\" Academic Press, New York, N . Y . . 1966 . react iv i ty. This paper descr ibes studies of one such class: a lkoxides of copper( l ) . These studies had three object i ies: synthesis and character izat ion of a lkoxides und phenox ides o f copper ( l ) ; de termina t ion o f the behar l ior of thesc substances in react ions whose usefulness with alkylcopper reagents has already been establ ished: and examinat ion of the mechanisms of their thermal decomposi t ion. Copper( l ) a lkoxides and phenoxides have been impl icated previously as intermediates in a var iety of copper-catalyzed react ions,a '5 and poor ly character ized examples of these substances have been prepared'6 A useful synthesis of copper([) tert-butoxideT is not appl icable to the preparat ion of the thermal ly unstable copper( I ) pr imary and secondary alkoxides that were of ^central interest in our work. The preparat ion of copper( I ) phenoxide by a procedure analogous to that descr ibed here has been reported.s Copper( I ) a lkoxides (5) J. K. I (ochi , Proc. I t t t . Congr. Pure Appl ' Chem', 23rd,4 ' 377 (1971), and referenccs citcd therein, (6 ) b . E . H . Bawr r and F . J . Wh i tbv , J . Chem.9oc . ,3926 (1960) ; G ' Costa. A. Camus, and N. Marsich, J. Inorg ' l ' ' luc l ' Chem',27' 281 ( I e6s ) . (7) T. Saegusa, T. Tsucla, and T. Hashirnoto, J ' Amer ' Chem' Soc\" 94 ,658 (1972) . iSl f. I(awaki and H. Hashimoto, Bull. Chem. Soc' Jap', 45, 1499 (r972). Whitesides, et al, I St'nthesis ttf Cttpper(l) Alkoxides

Selectivity in organic group transfer in reactions of mixed lithium diorganocuprates

Abstract: Solut ions obtained by mix ing 1 equiv of organo( l igand)copper( I ) reagent (organo = n-buty l , sec-buty l , ter f butyl, phenyl, and 1-pentynyl) with 1 equiv ofan organolithium reagent having a different organic group have been allowed to react with 1-bromopentane, methyl vinyl ketone, and nitrobenzene. The relative yields of products observed in these reactions of \"mixed\" l ithium diorganocuprates, \"RrRzCuLi,\" are summarized and used to infer the relative reactivities of the two organic groups in these complexes. Organic moieties that form stable, unreact ive, copper( I ) compounds (1-pentynl ' I , fer f -butoxyl , ary l ) show the smal lest react iv i ty in these cuprates and are the most generally useful first components for mixed ate complexes in which it is intended that the second component react preierentially with substrate. However, use of these groups has one drawback in reactions involving certain substrates of low reactivity': the reactivity of the second organic group in the mixed complex is s igni f icant ly decreased bv inclusion in the complex, re lat ive to that which would be expected f rom the corresjonding symmetrical cuprate. If mixed cuprates made from stable organocopper compounds show insufficient react iv i t l ' . mixed complexes contain ing a highly basic organic group, part icular ly fer f -buty l , may have advantages. A survey of the re lat ive react iv i ty of several a lky l bromicles toward l i th ium di-n-buty lcuprate establ ishes a structure-rate prof i le for nucleophi l ic coupl ing character is t ic of an SN2 react ion.

Method of sepctral analysis using nmr shift reagents

Abstract: The ability of nuclear magnetic resonance spectroscopy to distinguish between compounds and between parts of compounds is substantially increased by the use of certain rare earth chelate shift reagents. The preferred shift reagents are the europium III chelates of substituted or unsubstituted dicampholyl ligands, and europium III chelates of substituted or unsubstituted nopinato compounds. The reagents are particularly useful in determining the enantiomeric purity of compositions containing mixtures of enantiomers.

Enzymatic Regeneration of ATP from AMP and ADP Part I. Thermodynamics, Kinetics, and Process Development

Abstract: Adenosine triphosphate (ATP) plays a prominent role in many biosynthetic pathways wherein chemical bonds are made which otherwise would not form in significant quantity in dilute aqueous solution. In such reactions the breakdown of ATP is coupled via a common intermediate with synthesis of the new chemical bond. The work reported here is part of a coordinated effort to demonstrate large-scale, cell-free enzymatic synthesis of useful products with simultaneous regeneration of the ATP consumed in the biosynthetic reaction.

Enzymatic Regeneration of ATP from AMP and ADP Part II : Enzyme Immobilization and Reactor Development

Abstract: The biosynthesis of many natural products consumes ATP (1). The involvement of ATP in biosynthetic reactions can be illustrated by two well established pathways for the activation of an alkyl carboxylate ion (Fig. 1). In one, transfer of the terminal phosphate Open image in new window Fig. 1 Pathways for Activation of Alkyl Carboxylate group of ATP to the carboxylate grouping (phosphoryl transfer) results in the production of an acyl phosphate and ADP. In a second pathway, nucleophilic attack of carboxylate ion on the α-phosphate grouping of ATP (adenylyl transfer) generates an acyl adenylate and inorganic pyrophosphate ion. These two types of acyl derivatives are both active esters and can take part in further reactions at the carbonyl group.

Process for producing ethynylating agents

Abstract: An ethynylating agent formed from mixing an anhydrous magnesium compound with sodium acetylide and its use in preparing ethynyl carbinols.

Mechanism of reaction of carbon monoxide with phenyllithium

Abstract: The product mixtures obtained by reaction between phenyllithium and carbon monoxide in diethyl ether, followed by hydrolysis, include benzophenone (1). a,a-diphenylacetophenone (2), benzil (3), a,a-diphenyl- a-hydroxyacetophenone (4), benzpinacot (5), a-hydroxyacetophenone (6), 1,3,3-triphenylpropane-1,2-dione (7), 1,3,3-triphenylpropan-1-one-2,3-diol (8). and benzhydrol (9). Compounds 1, 2, 6,7, and 8 are produced in signifi- cant yields i 3,4,5, and 9 are produced in trace quantities. Spectroscopic studies establish dilithium benzophenone dianion (18) as the first long-lived intermediate formed in this reaction; qualitative correlations between the basicity of a number of organolithium reagents and their reactivity toward carbon monoxide suggests, but does not prove, that benzoyllithium is a precursor of 18. Labeling experiments indicate that the products ultimately isolated following hydrolysis of the reaction mixture are derived from at least two pathways which compete for the initially formed 18. One involves combination of l8 with 1 equiv of phenyllithium and 1 equiv of carbon monoxide, followed by elimination of I equiv of lithium oxide. yielding 17, the lithium enolate of 2; a second involves com- bination of 18 with 1 equiv of phenyllithium and 2 equiv of carbon monoxide. yielding 22,the trilithium trianion of 8. Hydrolysis of l7 yields 2 directly. Hydrolysis of 22 yields 8; reverse aldol reactions involving 8 or its pre- cursors generate 1 and 6. The mechanism proposed to account for the major products of the reaction of phenyl- lithium and carbon monoxide is outlined in Scheme III" On the basis of this scheme, plausible paths to the minor products of the reaction are proposed.