Insert select, with

Select a tungsten carbide insert bit with a medium offset and long chisel crested inserts when drilling sandy shale with limestone and dolomite. Use bits type 4-1 to 5-3. 

Select a tungsten carbide insert bit with a minimum offset and projectile or conical inserts when drilling limestone, brittle shale, nonporous dolomite and broken formations. Use bit type 6-3 to 7-3. 

Select a tungsten carbide insert bit with no offset and conical or double cone inserts when drilling hard and abrasive limestone, hard dolomite, chert, pyrite, quartz, basalt, etc. Use bit type 7-4 to 8-3. 

One of the most dramatic recent developments in metal carbene chemistry catalyzed by dirhodium(II) has been demonstration of the feasibility and usefulness of intermolecular carbon-hydrogen insertion reactions [38, 91]. These were made possible by recognition of the unusual reactivity and selectivity of aryl- and vinyldiazoacetates [12] and the high level of electronic control that is possible in their reactions. Some of the products that have been formed in these reactions, and their selectivities with catalysis by Rh2(S-DOSP)4, are reported in Scheme 10. 

There is some increase in selectivity with functionally substituted carbenes, but it is still not high enough to prevent formation of mixtures. Phenylchlorocarbene gives a relative reactivity ratio of 2.1 1 0.09 in insertion reactions with i-propylbenzene, ethylbenzene, and toluene.212 For cycloalkanes, tertiary positions are about 15 times more reactive than secondary positions toward phenylchlorocarbene.213 Carbethoxycarbene inserts at tertiary C—H bonds about three times as fast as at primary C—H bonds in simple alkanes.214 Owing to low selectivity, intermolecular insertion reactions are seldom useful in syntheses. Intramolecular insertion reactions are of considerably more value. Intramolecular insertion reactions usually occur at the C—H bond that is closest to the carbene and good yields can frequently be achieved. Intramolecular insertion reactions can provide routes to highly strained structures that would be difficult to obtain in other ways. 

As a tool to improve the regio- and stereoselectivity of C-H insertion, activation of a specific C-H bond of substrates to be inserted seems to be appropriate in conjunction with the manipulation of carbene character. These two tools for the improvement of insertion selectivity will provide us with useful tools of the C-C bond formation by carbenes and carbenoids. 

Use of Rh2(OAc)4 suggested that there was no inherent selectivity attributable to the coordinated carbene or to rhodium(ll). However, modification of dirhodium(ll) ligands to imidazolidinones provided exceptional diastereocontrol, obtained by influencing the conformational energies of the intermediate metal carbene [19, 23], as well as high enantiocontrol. Representative examples of products from these highly selective intramolecular C-H insertion reactions with cyclic systems is given in Scheme 15.6. Additional examples of effective insertions in systems from which diastereomeric products can result are illustrated in processes of the synthesis of 2-deoxyxylolactone (Scheme 15.7) [64, 65]. Here the conformation of the reactant metal carbene that is responsible for product formation is 32 rather than 33. Other examples in non-heteroatom-bound systems (for example, as in Eq. 15) confirm this preference. 

The insertion of allenes in the palladium-carbon a bond of cyclopalladated pyridine derivative 295 (cf. 00CRV3067) affords stable, isolable (ry -allyl) palladium complexes (e.g., 296) (03JOM(687)313). The ideally located imine unit when depalladated reacts selectively with the allyl functionality to yield methylene morphanthridizinium salts 297a-c. 

The relatively high tendency of aluminium alkyls to undergo j -hydrogen transfer, coupled with olefin insertion barriers that are much higher than those for transition metals, makes it unlikely that very efficient high-MW olefin polymerization catalysts based on aluminium will be discovered. Even for the reaction of aluminium alkyls with ketones, using ligands to tune towards insertion selectivity will be difficult. 

Furthermore, specific mineral matrices for use in conditioning separated radio nuclides are also elaborated and studied on the basis of mineral structures, known in nature for their selective-insertion capabihties with respect to certain radio nuclides and their stabihty over time. Among those phases, hollandite, zirconoUte, apatite and monazite are particularly studied. 

The carbene insertion of the aryldiazoacetate 78 onto the 2-position of iV-Boc-piperidine is highly selective with Rh catalysis <99JA6509, 99JA6511>. The enantiomeric excess could be easily increased to >95% by recrystallization. 

Other differences between singlet (concerted) insertion and triplet (abstraction-recombination) carbene insertion are seen in selectivity, stereochemistry, and the kinetic deuterium isotope effect. The triplet states are more selective in C—H insertion than the singlets. For example, the triplet shows higher tertiary to primary selectivity than the singlet in the insertion reaction with 2,3-dimethylbutane. Singlet carbene is shown to insert into C—H bond with retention of configuration, while racemization is expected for triplet insertion reaction from the abstraction-recombination mechanism. For example, the ratios of diastereomeric insertion product in the reaction of phenylcarbene with roc- and mcTO-2,3-dimethylbutanes are 98.5 1.5 and 3.5 96.5, respectively. ... 

Dirhodium(II) compounds are reported to be the most suitable catalysts for insertion. Selectivity is higher and yields are greater with dirhodium(II) carboxylates or carboxamidates than with copper catalysts, whereas Ru catalysts are not known to facilitate C-H insertion. As expected by a process that is basically electrophilic, electron-donating substituents that are adjacent to the site of insertion activate that center for C-H insertion ril4]. In addition to electronic influences, however, conformational effects that are basically steric in origin can also control reaction selectivity [115]. 

Cyclohexylisonitrile inserts selectively into the endocyclic vinyltitanium bond of a-methylenetitanacyclobutene complexes 37, although the reaction fails for many other isonitriles (Equation 12) <19960M1176>. No insertion occurs upon treatment with nitriles or ketones, in contrast to the established reactivity of typical titanacyclobutenes <1996CHEC-II(lb)887>. The reaction of fert-butylisonitrile with 1,9-anthracenediyl-zirconocene complex 38 proceeds exclusively by insertion into the terminal ring zirconium-carbon bond, presumably due to steric considerations (Equation 13) <2000JA9880>. 

Components of a photosystem can be inserted selectively into the lipid wall or the inner cavity of the vesicle. For this purpose the lipid and components insoluble in water are dispersed together in aqueous solution by sonification. This leads to an occlusion of water insoluble components within the lipid bilayer. The vesicle membrane is sufficiently stable and impermeable for a number of ions. This allows one to prepare, by gel-filtering, the media of different ionic composition inside and outside the vesicle as shown in Fig. 2b. Such asymmetry of chemical content can be preserved for a rather long time (from several hours to several days). Recently the surfactant molecules with double bonds, which can be polymerized after vesicle preparation, were used for further enhancement of vesicle stability [37-39]. Such polymerized vesicles are stable for several months. 

Studies aimed at the comparison of Rh(II) and Cu(II)-catalyzed onium ylide reactions of diazoketones 449 using 3 mol% of the former and 15 mol% of the latter led to the conclusion that the copper-catalyzed process provides the better yields and selectivities for [1,2]-rearrangement products 450 (Fig. 107) [490, 491]. In the rhodium-catalyzed process, 1,5-C-H insertion may compete. The diastereo-selectivity with both catalysts is in some cases similar, in others the Rh-catalyzed process is more selective. Analogous reactions of acetal 451 provided a mixture of stereoisomers 452a and 452b at the benzylidene position, supporting a stepwise process. The authors proposed that the involved intermediate was either a 1,6-biradical or the corresponding ion pair. 

Unsaturated acetals. Reaction of ethyl diazoacetate with dimethyl acetals of a,(3-unsaturated aldehydes catalyzed by BE, ethciate gives as the main product acetals of P. y-unsaturated aldehydes by a carbon-carbon insertion. A similar reaction with ketals gives a complex mixture. The reaction is less selective with diethyl acetals. 

---