Nitrogen addition

Of special importance is the complex problem of nitrogen addition as related to the dmg dopamine, where even model compounds lead to extremely complex chemistry and difficult analytical problems (65). 

Preparation—Cortexolone 1,21-Methyl Orthoacetate. A mixture of cortexolone (10 g), methyl orthoacetate (10 ml) dimetliylformamide (10 ml) and /)-toluenesulfonic acid (40 mg) is heated at 110-120° for 4 hr, the alcohol produced during the reaction being removed by a stream of nitrogen. Addition of a few drops of pyridine and evaporation under vacuum affords a residue which yields 7.8 g of product (67%), mp 174-176°, after trituration with methanol [a]o 92° (Diox). 

A constant nitrogen addition into the discharge line from the vacuum pump to the vacuum pump discharge drum/seal drum system. 

Nowhere, perhaps, is this phenomenon better illustrated than in the phenothiazine class. The earlier volume devoted a full chapter to the discussion of this important structural class, which was represented by both major tranquilizers and antihistamines. The lone phenothiazine below, flutiazin (130), in fact fails to show the activities characteristic of its class. Instead, the ring system is used as the aromatic nucleus for a nonsteroidal antiinflammatory agent. Preparation of 130 starts with formylation of the rather complex aniline 123. Reaction with alcoholic sodium hydroxide results in net overall transformation to the phenothiazine by the Smiles rearrangement. The sequence begins with formation of the anion on the amide nitrogen addition to the carbon bearing sulfur affords the corresponding transient spiro intermediate 126. Rearomatization... 

Several reviews on the synthesis of aziridines have been published in the previous year. These publications include a review on the silver catalyzed addition of nitrenes (among other intermediates such as carbene) across a double bond <06EJOC4313> a review on sulfur ylide addition to imines to form aziridines <06SL181> a review on nitrogen addition across double bonds <06ACR194> a general review on functionalization of a,p-unsaturated esters with some discussion of aziridination <06TA1465>... 

In most of these reactions, it is nitrogen of a urea, thiourea, isothiourea, or an amidine which is the nucleophile for the addition to an appropriately situated electrophilic carbon. Conditions which enhance the electrophilic character of the carbon, or the nucleophilicity of the nitrogen, promote cyclization. Most commonly, this cyclization is affected by nitrogen addition to the electrophilic / -carbon of a Michael acceptor, and can be performed under acid or basic conditions. 

Harmata et al. have developed a tandem Sonogashira/nitrogen-addition reaction of acetylenes 261 to sulfonamide 262 to prepare S(vi)-oxidized compounds 263 and 264 (Scheme 36) <20050L143>. When R = alkyl (e.g., Pr"), the 1,2-thiazine 263 is the major product (70%) formed via a endocyclization process, along with a minor amount (20%) of exocyclized product 264, while the five-membered ring product 264 (81%) is preferred when R= Ph. 

Six different fish samples were analyzed for As species by Branch et al. [76]. Five species were separated [AB, DMA, As(III), MMA and As(V)] using a Benson strong anion-exchange resin. The predominant arsenic compound was found to be AB which is non-toxic. Arsenic levels were in the range 1.0 mg kg-1 dry mass in mackerel to 187 mg kg-1 dry mass in plaice. Nitrogen addition was used to remove ArCl+ interference at m/z 75. 

David, M., B. A. M. Cupples, G. B. Lawrence, G. Shi, K. Vogt, and P. M. Wargo. 1998. Effect of chronic nitrogen additions on soil nitrogen fractions in red spruce stands. Water, Air and Soil Pollution 105 183-192. 

Catledge, S., and Vohra, Y., Effect of nitrogen addition on the microstructure and mechanical properties of diamond films grown using high-methane concentrations. /. App. Phys. 86 (1), 698-700 (1999). 

Like oxygen, sulfur is more electronegative than nitrogen. Additionally, sulfur is more polarizable. These differences stabilize the sulfur anion as reflected in the pKa value for methyl sulfide (10.4) compare to the pKa value for amines (35). Therefore, the methylsulfide anion is the better leaving group. 

Lack of space prevents descriptions of a number of additional types of boron compounds such as the numerous interstitial metallic borides, the subhalides (of type B2CI4), the organoboron compounds (such as B(CH3)3), and the boron-nitrogen addition compounds, many of which have been prepared by H. C. Brown to study the effects of structures on the stability of Lewis acid-base adducts. ... 

Evangelou, V. P. and R. L. Blevins. 1988. Effect of long-term tillage systems and nitrogen addition on quantity-intensity relationships Q/I in long-term tillage systems. Soil Sci. Soc. Am. J. 52 1047-1054. 

---